Add integration tests for resource service auth

[drewnoakes]

Following #3033 and #3400, we need integration test coverage for auth between the dashboard and a resource service.

This includes both API-key and certificate based auth. We don't currently ship a resource service that uses certificates, so we'd likely need to mock one for test purposes.

• Unsecured Add resource service auth tests (Unsecured, ApiKey) #3824
• ApiKey Add resource service auth tests (Unsecured, ApiKey) #3824
• Certificate

[kvenkatrajan]

@drewnoakes - are all the scenarios covered with #3824 ?

[drewnoakes]

This was duped in #3739. Closing this as a dupe.