HTTPRouteRequestMultipleMirrors conformance test has invalid backendRef

[frankbu]

What happened:

Running the HTTPRouteRequestMultipleMirrors conformance test fails because the second mirrored backendRef is in a different namespace:

gateway-api/conformance/tests/httproute-request-multiple-mirrors.yaml

Line 25 in 759e09e

namespace: another-namespace

What you expected to happen:

This failure is expected because:

1. there is no another-namespace namespace with the infra-backend-v3 service
2. even if there was, there is no ReferenceGrant to allow the cross ns request

As per BackendObjectRef doc:

If the referent cannot be found, this BackendRef is invalid and must be dropped from the Gateway. The controller must ensure the “ResolvedRefs” condition on the Route status is set to status: False and not configure this backend in the underlying implementation.

If there is a cross-namespace reference to an existing object that is not allowed by a ReferenceGrant, the controller must ensure the “ResolvedRefs” condition on the Route is set to status: False, with the “RefNotPermitted” reason and not configure this backend in the underlying implementation.

How to reproduce it (as minimally and precisely as possible):

Run the conformance test with any compliant gateway implementation.

Anything else we need to know?: