Better auth mechanism

[adri]

Change the API to also allow other apps to authenticate.

Maybe we can use https://developers.google.com/+/mobile/ios/sign-in to automatically sign in with the google account and then authenticate with that against the API.

There is a homeServerClientID which can be set when signing in and results in a homeServerAuthorizationCode. Maybe on the API level this can be used to login on the server.

There is a rect native version. https://github.com/apptailor/react-native-google-signin

[adri]

https://developers.google.com/identity/sign-in/ios/offline-access
https://developers.google.com/identity/sign-in/android/offline-access
https://developers.google.com/api-client-library/php/guide/aaa_idtoken