Update an app user by ID. Only the fields specified in the update mask are updated. Currently, only the appUserType, and identityUserId fields can be updated.
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
This API uses OAuth2 with the Client Credential flow. Client Credentials must be sent in the BODY, not the headers. For an example of how to implement this, refer to the c1TokenSource.Token() function.
The ID of the application.
A unique idenditfier of the application user.
The AppUserServiceUpdateRequest message contains the app user and the fields to be updated.