Feature Request: Automate ReferenceGrant Creation When Using HTTPRoute with Gateway API in Flagger

[kahirokunn]

Describe the feature

What problem are you trying to solve?

When using Flagger with the Gateway API to create HTTPRoutes, users must currently create a ReferenceGrant manually to allow cross-namespace references between the HTTPRoute and the relevant resources (such as Gateways). This manual step adds overhead, and missing a ReferenceGrant can lead to configuration issues and delays in setup.

Proposed solution

Implement functionality in Flagger to automatically create a ReferenceGrant whenever an HTTPRoute is created with a cross-namespace reference requirement. This automation would simplify the process, minimize manual configuration, and reduce the likelihood of errors due to missing permissions.

Considered drawbacks

• This approach may add complexity to the Flagger codebase.

Any alternatives you've considered?

1. Manual Creation: Users can continue to create ReferenceGrants manually, but this approach is prone to user error and slows down deployment workflows.
2. CLI Tool: Providing a CLI tool or script to generate necessary ReferenceGrants could help, but it lacks the seamless experience of automated creation within Flagger itself.