Add changelog entry for version 8.15.0

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Add changelog entry for version 8.15.0

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Adds changelog entry for 8.15.0 release documenting merged PRs since 8.14.0

Description

Inserts 8.15.0 section above 8.14.0 in CHANGELOG.md with the following categories:

• New Features: ECDsa support in X509SecurityKey and JsonWebKeyConverter (Add ECDsa support in X509SecurityKey and JsonWebKeyConverter.ConvertFromX509SecurityKey #2377)
• Bug Fixes: Log sanitization (Sanitize logs #3316), SearchValues optimization (Optimize log sanitization with SearchValues for improved performance #3341), IDX10400 test update (Update test for IDX10400 #3314)
• Fundamentals: Algorithm tests, agent rules migration, TestExtensions System.Text.Json migration, code coverage configuration, CodeQL fixes
• .NET 10 / SDK updates: Preview/RC1 compatibility, test execution consistency, workflow updates, CG compliance, tooling updates (Coverlet, test SDK, runTests.ps1)
• Documentation: Support policy updates (Update supportPolicy.md #3367)

Follows existing changelog format with bold headers, two-space indentation, and PR reference links.

Original prompt

Add a new changelog entry for version 8.15.0 to CHANGELOG.md, targeting the dev branch.

Context:

• The changelog should follow the existing format and style used in recent entries (e.g., 8.12.0–8.14.0) with sections such as "New Features", "Bug Fixes", "Fundamentals", and any relevant subheadings.
• The new 8.15.0 section must be inserted immediately above the existing 8.14.0 section in CHANGELOG.md.
• Use the following prepared text for the 8.15.0 entry (you may adjust wrapping/indentation to match the file, but do not change wording except for trivial formatting):

8.15.0
====
## New Features
- **Add ECDsa support in `X509SecurityKey` and `JsonWebKeyConverter.ConvertFromX509SecurityKey`**  
  Extended `X509SecurityKey` and `JsonWebKeyConverter.ConvertFromX509SecurityKey` to support ECDSA keys.  
  See PR [#2377](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/2377) for details.

## Bug Fixes
- **Sanitize logs to avoid leaking sensitive data**  
  Updated logging to sanitize sensitive values, reducing the risk of inadvertently exposing secrets or PII in logs.  
  See PR [#3316](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3316) for details.
- **Optimize log sanitization with `SearchValues`**  
  Improved the performance of the log sanitization logic introduced earlier by using `SearchValues`, making sanitization more efficient in high-throughput scenarios.  
  See PR [#3341](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3341) for details.
- **Update test for `IDX10400`**  
  Adjusted the `IDX10400` test to align with the current behavior and error messaging.  
  See PR [#3314](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3314) for details.

## Fundamentals
- **Add supported algorithm tests**  
  Added new tests to validate the set of supported cryptographic algorithms, increasing confidence in algorithm coverage and compatibility.  
  See PR [#3296](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3296) for details.
- **Migrate repository agent rules from `.clinerules` to `agents.md`**  
  Moved repository agent/AI-assist rules into markdown documentation to make them more visible and easier to maintain.  
  See PR [#3313](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3313) for details.
- **Migrate `Microsoft.IdentityModel.TestExtensions` from Newtonsoft.Json to System.Text.Json**  
  Updated `Microsoft.IdentityModel.TestExtensions` to use `System.Text.Json` instead of `Newtonsoft.Json`, aligning tests with the runtime serialization stack.  
  See PR [#3356](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3356) for details.
- **Disable code coverage comments**  
  Turned off automated code coverage comments on PRs to reduce noise while retaining coverage data elsewhere.  
  See PR [#3349](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3349) for details.
- **Fix CodeQL alerts**  
  Addressed CodeQL-reported issues to improve security posture and static analysis cleanliness.  
  See PR [#3364](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3364) for details.

### .NET 10 / SDK and tooling updates
- **Building with .NET 10 preview / RC 1**  
  Updated the repository to build and test against .NET 10.0 preview/RC1, ensuring early compatibility with the upcoming runtime.  
  See PRs [#3287](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3287), [#3357](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3357), and [#3358](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3358) for details.
- **Fix .NET 10 test execution consistency**  
  Ensured consistent use of the `TargetNetNext` parameter across build, test, and pack phases so .NET 10.0 tests execute reliably.  
  See PR [#3337](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3337) for details.
- **Update project files and workflows for .NET 10.0 compatibility**  
  Adjusted project files and CI workflows to correctly target and run on .NET 10.0, including test and pack scenarios.  
  See PR [#3363](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3363) for details.
- **Update .NET version to meet CG compliance**  
  Updated the .NET version references to be compliant with corporate governance (CG) requirements.  
  See PR [#3353](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3353) for details.
- **Update Coverlet collector and test SDK**  
  - Bumped `CoverletCollectorVersion` to 6.0.4.  
    See PR [#3333](https://g...

</details>

*This pull request was created as a result of the following prompt from Copilot chat.*
> Add a new changelog entry for version 8.15.0 to CHANGELOG.md, targeting the dev branch.
> 
> Context:
> - The changelog should follow the existing format and style used in recent entries (e.g., 8.12.0–8.14.0) with sections such as "New Features", "Bug Fixes", "Fundamentals", and any relevant subheadings.
> - The new 8.15.0 section must be inserted immediately above the existing 8.14.0 section in CHANGELOG.md.
> - Use the following prepared text for the 8.15.0 entry (you may adjust wrapping/indentation to match the file, but do not change wording except for trivial formatting):
> 
> ```markdown
> 8.15.0
> ====
> ## New Features
> - **Add ECDsa support in `X509SecurityKey` and `JsonWebKeyConverter.ConvertFromX509SecurityKey`**  
>   Extended `X509SecurityKey` and `JsonWebKeyConverter.ConvertFromX509SecurityKey` to support ECDSA keys.  
>   See PR [#2377](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/2377) for details.
> 
> ## Bug Fixes
> - **Sanitize logs to avoid leaking sensitive data**  
>   Updated logging to sanitize sensitive values, reducing the risk of inadvertently exposing secrets or PII in logs.  
>   See PR [#3316](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3316) for details.
> - **Optimize log sanitization with `SearchValues`**  
>   Improved the performance of the log sanitization logic introduced earlier by using `SearchValues`, making sanitization more efficient in high-throughput scenarios.  
>   See PR [#3341](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3341) for details.
> - **Update test for `IDX10400`**  
>   Adjusted the `IDX10400` test to align with the current behavior and error messaging.  
>   See PR [#3314](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3314) for details.
> 
> ## Fundamentals
> - **Add supported algorithm tests**  
>   Added new tests to validate the set of supported cryptographic algorithms, increasing confidence in algorithm coverage and compatibility.  
>   See PR [#3296](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3296) for details.
> - **Migrate repository agent rules from `.clinerules` to `agents.md`**  
>   Moved repository agent/AI-assist rules into markdown documentation to make them more visible and easier to maintain.  
>   See PR [#3313](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3313) for details.
> - **Migrate `Microsoft.IdentityModel.TestExtensions` from Newtonsoft.Json to System.Text.Json**  
>   Updated `Microsoft.IdentityModel.TestExtensions` to use `System.Text.Json` instead of `Newtonsoft.Json`, aligning tests with the runtime serialization stack.  
>   See PR [#3356](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3356) for details.
> - **Disable code coverage comments**  
>   Turned off automated code coverage comments on PRs to reduce noise while retaining coverage data elsewhere.  
>   See PR [#3349](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3349) for details.
> - **Fix CodeQL alerts**  
>   Addressed CodeQL-reported issues to improve security posture and static analysis cleanliness.  
>   See PR [#3364](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3364) for details.
> 
> ### .NET 10 / SDK and tooling updates
> - **Building with .NET 10 preview / RC 1**  
>   Updated the repository to build and test against .NET 10.0 preview/RC1, ensuring early compatibility with the upcoming runtime.  
>   See PRs [#3287](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3287), [#3357](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3357), and [#3358](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3358) for details.
> - **Fix .NET 10 test execution consistency**  
>   Ensured consistent use of the `TargetNetNext` parameter across build, test, and pack phases so .NET 10.0 tests execute reliably.  
>   See PR [#3337](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3337) for details.
> - **Update project files and workflows for .NET 10.0 compatibility**  
>   Adjusted project files and CI workflows to correctly target and run on .NET 10.0, including test and pack scenarios.  
>   See PR [#3363](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3363) for details.
> - **Update .NET version to meet CG compliance**  
>   Updated the .NET version references to be compliant with corporate governance (CG) requirements.  
>   See PR [#3353](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3353) for details.
> - **Update Coverlet collector and test SDK**  
>   - Bumped `CoverletCollectorVersion` to 6.0.4.  
>     See PR [#3333](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3333) for details.  
>   - Upgraded `Microsoft.NET.Test.Sdk` to a newer version for improved test reliability and tooling support.  
>     See PR [#3336](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3336) for details.
> - **Update `runTests.ps1` to specify dotnet directory**  
>   Updated `runTests.ps1` to accept an explicit dotnet directory, improving test execution robustness in environments with multiple SDK installations.  
>   See PR [#3368](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3368) for details.
> - **Adjust dotnetcore workflow targeting for .NET 10 SDK**  
>   Iterated on the CI workflow configuration to correctly target the .NET 10 SDK:  
>   - Temporarily removed targeting of the .NET 10 SDK in `dotnetcore.yml`.  
>     See PR [#3335](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3335).  
>   - Reverted that change to restore .NET 10 SDK targeting.  
>     See PR [#3339](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3339) for details.
> 
> ### Documentation
> - **Update support policy documentation**  
>   Refreshed `supportPolicy.md` to reflect the latest support policy for IdentityModel.  
>   See PR [#3367](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/pull/3367) for details.
> ```
> 
> Requirements:
> - Base branch: dev
> - Create a new branch, apply the above CHANGELOG.md update, and open a pull request.
> - Use a concise, descriptive title, e.g., "Changelog for 8.15.0".
> - In the PR description, mention that this adds the 8.15.0 changelog entry based on the list of merged PRs since 8.14.0.

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