Evaluate Next Gateway API Release for Updates to NGF

[mpstefan]

Spike to evaluate the next release of the Gateway API and to create a list of issues to implement to ensure we have core support for the next version.

[kate-osborn]

TLDR - so far there's nothing critical that we have to implement for the upcoming release.

New to experimental channel:

• Gateway infrastructure (core). Only applies to controllers that provision resources.
• Gateway listener tls frontend validation (extended)
• Session persistence for http and grpc routes (extended)
• Backend LB policy (extended)
• Named routing rules for all route types
• Supported Features. Not new, but breaking changes have been made. We don't currently implement supported features, so this change doesn't affect us.

New to standard:

• HTTPRoute timeouts (extended)
• Increased the limit on HTTPRoute matches for 8 to 64. Total number of matches across all rules in a route must be less than 128.
• When an HTTPBackendRef refers to a Service that has no ready endpoints, implementations should return a 503.
• Backend protocol selection (extended)

What might make it to standard:

• Gateway infrastructure
• Timeouts and duration

What might make it to experimental:

• Percentage-based request mirroring
• Configurable retries

Conformance tests are passing on main which means we should be good for the release unless anything changes in the next month.

Here's a list of the extended features we do NOT support for the Gateway-HTTP conformance profile:

• GatewayHTTPListenerIsolation
• GatewayInfrastructurePropagation
• GatewayStaticAddresses
• HTTPRouteBackendProtocolH2C
• HTTPRouteBackendProtocolWebSocket
• HTTPRouteBackendRequestHeaderModification
• HTTPRouteBackendTimeout
• HTTPRouteParentRefPort
• HTTPRoutePathRedirect
• HTTPRouteRequestMirror
• HTTPRouteRequestMultipleMirrors
• HTTPRouteRequestTimeout

Recommended changes we should make for the upcoming release:

• Test new limits on HTTPRoute matches. We should allow a rule with up to 64 matches.
• When an HTTPBackendRef refers to a Service that has no ready endpoints, we should return a 503. Currently, we return a 502.

[kate-osborn]

Created #2431 and #2430