Added JWT_decode. Prefixed all functions with "fn_" (for the sake of…

[johnjarrard]

… clarity). Added Fn_Split to use with fn_JWT_Decode

[chrisblatchley]

Looks great. I no longer work for this company so I can't merge it in. Also, the fn_ prefix isn't how Veracross does user defined functions so it unfortunately might not get merged in for that reason. However, I'll star your fork.

[sixfeetover]

@johnjarrard Thanks! I'd gladly pull in the new functions; however, as Chris mentioned we don't prefix functions with fn_ here. We also use lowercase for keywords - updating the formatting of Split to match the rest of the project would be helpful.

If you want to submit just the enhanced functionality without the fn_ rename, I'll merge.

[Imran-imtiaz48]

This PR introduces several improvements and refactoring in the jwt.sql file. The changes include:

• Creation of new, consistently named scalar functions (fn_Split, fn_XmlToJson, fn_HMAC, fn_Base64, fn_Base64ToBinary, fn_JWT_Encode, fn_JWT_Decode)
• Renaming all functions to use the fn_ prefix for clarity and consistency
• Addition of a new fn_Split function for string splitting
• Addition of a new fn_Base64ToBinary function with URL-safe decoding support
• Implementation of a new fn_JWT_Decode function for JWT parsing and validation
• Refactor of all function calls in the JWT encode/decode logic to use the new names
• Dropping and re-granting execute permissions on all updated functions
• Updated example usage (commented out) for the new function names

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Strengths

• Modularity & Consistency: The use of the fn_ prefix improves naming conventions, making the codebase easier to navigate and maintain.
• New Functionality: The addition of fn_Split, fn_Base64ToBinary, and fn_JWT_Decode extends the capabilities of this SQL JWT implementation, making it more feature-complete.
• Security: The decode function properly verifies the signature, returning an error JSON object if verification fails.
• Clean-up: Old function names are dropped before recreating, preventing duplicates or conflicts.
• Permissions: The script consistently grants execute permissions after each function definition.

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Suggestions

1. Documentation:

   • Consider adding more comments or a brief documentation section at the top of the file explaining the purpose of each function, especially the new ones.
   • Document the expected inputs/outputs for each function for easier onboarding of new contributors.

2. Error Handling:

   • In fn_JWT_Decode, the error message is hardcoded as a JSON string. You might want to consider standardizing error responses across all functions for consistency.

3. Testing:

   • If not already present, add unit tests or usage examples for the new functions (especially fn_Split, fn_Base64ToBinary, and fn_JWT_Decode).
   • Ensure the JWT decode/encode roundtrip works as expected with various payloads, secrets, and edge cases.

4. Performance:

   • For large payloads or high throughput scenarios, review the performance of string operations (especially in fn_Split). If this will be used in production with significant volume, consider potential optimizations.

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