Minor - P4 AuthorizationSessionImpl has the following constructor definition:
struct InstallMockForTestingOrAuthImpl {
explicit InstallMockForTestingOrAuthImpl() = default;
};
explicit AuthorizationSessionImpl(std::unique_ptr<AuthzSessionExternalState> externalState,
InstallMockForTestingOrAuthImpl);
There is one constructor, and it never uses InstallMockForTestingOrAuthImpl. All callers have to supply InstallMockForTestingOrAuthImpl.
Because this argument doesn't seem to affect the system, we should remove it.