Flie refactor

Pull request for challenge [30047592](https://www.topcoder.com/challenge-details/30047592/?type=develop)
The return schema should not be the resource.  It should match the other returns.  The FileActionResource was to be used as the content.

Take a look at the ChallengeResponse:  https://github.com/appirio-tech/lc1-challenge-service/blob/master/api/swagger/swagger.yaml#L1683  Follow this pattern but use FileActionResource instead of ChallengeResource