api: add BackendConfigPolicy api for configuring envoy clusters

[puertomontt]

Description

Introduce BackendConfigPolicy api to allow configuring envoy clusters. This PR ports the connection config from gloo. This is part of the "policy parity" effort, to have same functionality as Gloo apis.

#11167
#11203

Change Type

/kind new_feature

Changelog

Introduce BackendConfigPolicy api to allow configuring envoy clusters.

Additional Notes

[Copilot]

Pull Request Overview

Introduce the BackendConfigPolicy API to allow configuring Envoy clusters by porting Gloo’s connection config.

• Extend clientset, CRDs, RBAC, and applyconfiguration to support BackendConfigPolicy resources.
• Add sample testdata, translation logic, and plugin implementation for Envoy cluster generation.
• Include unit tests for translation and header-format handling.

Reviewed Changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
pkg/client/clientset/versioned/typed/api/v1alpha1/api_client.go	Add BackendConfigPolicies getter to clientset
internal/kgateway/wellknown/kgw.go	Register GVK/GVR for BackendConfigPolicy
internal/kgateway/setup/testdata/standard/backendconfigpolicy.yaml	Add sample BackendConfigPolicy input YAML
internal/kgateway/setup/testdata/standard/backendconfigpolicy-out.yaml	Expected Envoy config output for policy
internal/kgateway/extensions2/registry/registry.go	Register BackendConfigPolicy plugin
internal/kgateway/extensions2/plugins/backendconfigpolicy/plugin.go	Implement policy translation and processing
internal/kgateway/extensions2/plugins/backendconfigpolicy/plugin_test.go	Add unit tests for BackendConfigPolicy plugin
install/helm/kgateway/templates/role.yaml	Update RBAC rules for BackendConfigPolicy
install/helm/kgateway-crds/templates/gateway.kgateway.dev_backendconfigpolicies.yaml	Add CRD for BackendConfigPolicy
api/v1alpha1/zz_generated.register.go	Register BackendConfigPolicy types
api/v1alpha1/zz_generated.deepcopy.go	Autogen deepcopy funcs for BackendConfigPolicy
api/v1alpha1/backend_config_policy_types.go	Define BackendConfigPolicy spec and status types
api/applyconfiguration/utils.go	Support applyconfiguration for BackendConfigPolicy and related types

Comments suppressed due to low confidence (1)

internal/kgateway/extensions2/plugins/backendconfigpolicy/plugin_test.go:44

• Consider adding a test case for the DropHeadersWithUnderscores action in CommonHttpProtocolOptions to verify it maps to HttpProtocolOptions_DROP_HEADER correctly.

HeadersWithUnderscoresAction: ptr.To(v1alpha1.AllowHeadersWithUnderscores),

[lgadban]

just a few nits but overall this looks really solid!

did you do any manual testing?
I don't think these types of config options warrant an e2e test but would be good to know that functional behavior was confirmed with a running envoy

[puertomontt]

@lgadban I did some manual testing to ensure envoy picks up the config

[lgadban]

all the e2e tests are failing for some reason, might need to merge latest main?

[lgadban]

LGTM!

Looking at this with fresh eyes, I think we should add a happy path e2e test.
Maybe we can tackle this in the follow-up work for targetSelector support or when adding additional config to this API?