app: register app authmode during setup

Fixes: http://camlistore.org/issue/439

Change-Id: I5d78f1fb764b83a0a9afc35b4ffb62a1a7934ed0

pkg/server/app/app.go

@@ -162,3 +162,10 @@ func (a *AppHandler) Start() error {
 func (a *AppHandler) Name() string {
 	return a.name
 }
+
+// AuthMode returns the app handler's auth mode, which is also the auth that the
+// app's client will be configured with. This mode should be registered with
+// the server's auth modes, for the app to have access to the server's resources.
+func (a *AppHandler) AuthMode() auth.AuthMode {
+	return a.auth
+}

pkg/serverinit/serverinit.go

@@ -341,6 +341,7 @@ func (hl *handlerLoader) setupHandler(prefix string) {
 			exitFailure("error setting up app for prefix %q: %v", h.prefix, err)
 		}
 		hh = ap
+		auth.AddMode(ap.AuthMode())
 	} else {
 		var err error
 		hh, err = blobserver.CreateHandler(h.htype, hl, h.conf)