Initial Kgateway Provider Support

[danehans]

What type of PR is this?
/kind feature

What this PR does / why we need it:

Allows users to convert Ingress resources with Ingress NGINX-specific annotations (currently only nginx.ingress.kubernetes.io/client-body-buffer-size) into Gateway API + Kgateway TrafficPolicy.

Which issue(s) this PR fixes:

Fixes #260

Does this PR introduce a user-facing change?:

Adds provider "kgateway". This provider acts as an output implementation provider as apposed to the traditional provider that is used as a source.

[k8s-ci-robot]

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[danehans]

I wanted to share this approach before getting too deep into the implementation. Looking for feedback from maintainers.

[k8s-ci-robot]

@danehans: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-ingress2gateway-verify	5069ab4	link	true	/test pull-ingress2gateway-verify

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[Stevenjin8]

Yeah I read briefly through the PR and I think we should take a step back. As I understand this PR, when using the kgateway effectively translates ingress + a specific ingress-nginx annotation to kgw. I would much rather see a generic approach.

[LiorLieberman]

Thanks @danehans !

We had a break room session over kubecon - and the general ask was to agree on some foundational direction for this repo. @Stevenjin8 took this initiative and have some initial draft here

The main point to discuss is whether ingress2gateway is the place to host all this vendored code or we should have some other extensibility in place. I do know the urgency here, so hoping we can get agreements and collaboration here fast.

The main concern is maintainability.

Some prior art all points the direction of removal third party code from kubernetes.

@rikatz pointed out one example.

On Kubernetes we avoid vendor specific code and tend to have it as third party repos - See the removal of CSI drivers from core Kubernetes code, for instance

[danehans]

Closing in favor of #262 (implementation-specific emitters).

[danehans]

The main point to discuss is whether ingress2gateway is the place to host all this vendored code or we should have some other extensibility in place. I do know the urgency here, so hoping we can get agreements and collaboration here fast.
The main concern is maintainability.

I completely agree that a solution must be maintainable. I'm hoping #262 is an approach that the community feels will meet this goal.