Description:
Gateway operators may want to attach common policies to a group of gateways. Currently, duplicated instances of a policy need to be created and attached to each Gateway to achieve this. This can lead to significant configuration duplication, especially when many virtual gateways are merged to a single envoy deployment.

EnvoyPatchPolicy introduced a concept of GatewayClass-atttached policies for the merge gateways scenario.

This form of attachment can be extended to other policies like ClientTrafficPolicy, BackendTrafficPolicy, SecurityPolicy, EnvoyExtensionPolicy and BackendTLSPolicy.