If a user has access to multiple backend systems (a Production and a Staging environment), can he/she login with client credentials to a specific system? It seems there's nothing to indicate which system the client_id/secret should go to when generating the credentials from My Applications menu.
With (languagecloud.sdl.com/.../api it is possible to pass the name of the backend implementation against which authentication should occur using the 'implementation' parameter. This value will identify either Production or Staging using the TMS SystemName and ManTra will check the credentials on only the supplied TMS instance.
You can find below an example of an HTTP call to authenticate a user with ManTra using the TMS implementation:
POST /tm4lc/api/v1/auth/token HTTP/1.1Host: languagecloud.sdl.comContent-Type: application/x-www-form-urlencoded