anchor.diff:              - `USER_CREATE_INVALID_USERNAME` if the supplied `username` does not match the given criteria (regex: ^[a-zA-Z0-9\-\.]{3,20}$)
               - `USER_CREATE_INVALID_PASSWORD` if the supplied `password` does not satisfy the given criteria (regex: ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)[a-zA-Z\d]{8,}$)
               - `USER_CREATE_INVALID_EMAIL` if the supplied `email` is not a valid email
  +            - `REQUEST_UNSUPPORTED_CONTENT_TYPE` if the submitted content and/or Content-Type is not `application/json`
   
   + Response 422 (application/json)
       + Attributes (object)
  
positive.code:             A comprehensive list of possible errors:
              - `AUTH_MISSING_USERNAME` if no input for `username` was submitted
              - `AUTH_MISSING_PASSWORD` if no input for `password` was submitted
  
  + Response 401 (application/json)
      + Attributes (object)
  
negative.code:             - `USER_UPDATE_INVALID_PASSWORD` if the supplied `password` does not satisfy the given criteria (regex: ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)[a-zA-Z\d]{8,}$)
              - `USER_UPDATE_INVALID_EMAIL` if the supplied `email` is not a valid email
              - `USER_UPDATE_INVALID_RANK` if the supplied `rank` is not a valid rank (regex: ^[1-3]$)
              - `REQUEST_UNSUPPORTED_CONTENT_TYPE` if the submitted content and/or Content-Type is not `application/json`
  
  + Response 401 (application/json)
      + Attributes (object)
  