drive, googlephotos: warn when using rclone's shared client_id #9580

The shared Google Drive and Google Photos client_id is being retired and
will stop working during 2026. Warn users who rely on it (ie who have not
configured their own client_id) so they can create their own in advance.

The warning is only shown for auth flows that actually use the shared
client_id, not for service account, environment or anonymous auth.

See: https://forum.rclone.org/t/google-drive-and-google-photos-users-action-required/54005

backend/googlephotos/googlephotos.go

@@ -349,6 +349,8 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 		return nil, err
 	}
 
+	oauthutil.SharedClientIDWarning(name, "Google Photos", "https://rclone.org/googlephotos/#making-your-own-client-id", m)
+
 	baseClient := fshttp.NewClient(ctx)
 	oAuthClient, ts, err := oauthutil.NewClientWithBaseClient(ctx, name, m, oauthConfig, baseClient)
 	if err != nil {