[TCGC] [Bug] response/request header schema should not be generated

[haolingdong-msft]

Issue

For below case, RepeatabilityResult is as response header model, and should not be generated. But TCGC returns access for the model as public and usage = 4, thus after adopting TCGC access and usage, it gets generated.

alias RepeatableOperationsWithTraits = global.Azure.Core.ResourceOperations<SupportsRepeatableRequests &
  NoConditionalRequests &
  NoClientRequestId>;

op repeatableAction is RepeatableOperationsWithTraits.ResourceAction<
  User,
  BodyParameter<UserActionParam>,
  UserActionResponse
>;

/**
 * Provides repeatable request headers for requests and responses.
 * @template VersionAdded The version when the trait was added to the specification.
 *           Leave this empty if the trait is always supported.
 */
@trait("RepeatableRequests")
@traitAdded(VersionAdded)
model SupportsRepeatableRequests<VersionAdded extends EnumMember | null = null> {
  #suppress "@azure-tools/typespec-providerhub/no-inline-model" "This inline model is never used directly in operations."
  @traitContext(
    TraitContext.Create | TraitContext.Update | TraitContext.Delete | TraitContext.Action
  )
  repeatableRequests: {
    @traitLocation(TraitLocation.Parameters)
    parameters: RepeatabilityRequestHeaders;

    @traitLocation(TraitLocation.Response)
    response: RepeatabilityResponseHeaders;
  };
}

  @doc("Provides the 'Repeatability-*' headers to enable repeatable requests.")
  model RepeatabilityResponseHeaders {
    @visibility("read")
    @header("Repeatability-Result")
    @doc("Indicates whether the repeatable request was accepted or rejected.")
    repeatabilityResult?: RepeatabilityResult;
  }

detailed test case

Solution

TCGC return usage as 0 to indicate the model should not be generated.