Google Cloud Endpoints v2 with firebase and retrofit

Question

I want to protect my API methods with user authentication. The best fit for Android app seemed to be a firebase authentication, which I'm using. Now, how do I call my API methods using retrofit or even curl with authenticated firebase user.

I've followed the example from here and added following API method:

@ApiMethod(
            path = "firebase_user",
            httpMethod = ApiMethod.HttpMethod.GET,
            authenticators = {EspAuthenticator.class},
            issuerAudiences = {@ApiIssuerAudience(name = "firebase", audiences = {PROJECT_ID})}
    )
    public Translation getUserEmailFirebase(User user) throws UnauthorizedException {
        if (user == null) {
            throw new UnauthorizedException("Invalid credentials");
        }
        return new Translation();
    }

Now, how it should be called? I've tried

curl \
     -H "Authorization: my-firebase-user-token-id" \
   https://my-api-link.appspot.com/_ah/api/something/v1/firebase_user

but I receive

{
     "error": {
      "errors": [
       {
        "domain": "global",
        "reason": "required",
        "message": "Invalid credentials"
       }
      ],
      "code": 401,
      "message": "Invalid credentials"
     }
    }

Answer 1

Using retrofit I had to add @Header("Authorization") String token to the api method param and in the code "Bearer " + token as a token.