Add unit tests for ResourceValidationHelper's usage of AipiService

Has to be done before the next release. Now that nothing is blocking this anymore, it should be easy to write a simple PR for this. Might also be a good idea to test that AIPI, if enabled, is actually being used in places where `ResourceValidationHelper` is being used on images (currently it's only level icons when publishing, user face icons and profile icon when updating user in-game, photo images when uploading a photo in-game).