Fetch api tokens in a separate request

Instead of sending a token with the application view (which is really
more of a session state view), fetch it separately using the tokenUrl
option of the Auth plugin. Account for the case where known personas
could change in the future without invalidating the current persona
and reset the Auth plugin whenever the persona in use changes. Use the
persona parameter to the token endpoint to get the appropriate token.

h/js/controllers.coffee

@@ -28,40 +28,38 @@ class App
     {plugins, host, providers} = annotator
 
     $scope.$watch 'auth.personas', (newValue, oldValue) =>
-      unless newValue?.length
-        authentication.persona = null
-        authentication.token = null
+      if newValue?.length
+        unless $scope.auth.persona and $scope.auth.persona in newValue
+          $scope.auth.persona = newValue[0]
+      else
+        $scope.auth.persona = null
 
     $scope.$watch 'auth.persona', (newValue, oldValue) =>
-      if oldValue? and not newValue?
-        if annotator.discardDrafts()
-          # TODO: better knowledge of routes
-          authentication.$logout => $scope.$broadcast '$reset'
-        else
-          $scope.auth.persona = oldValue
-      else if newValue?
-        $scope.sheet.collapsed = true
+      $scope.sheet.collapsed = true
+
+      unless annotator.discardDrafts()
+        $scope.auth.persona = oldValue
+        return
 
-    $scope.$watch 'auth.token', (newValue, oldValue) =>
       if plugins.Auth?
-        plugins.Auth.token = newValue
+        plugins.Auth.token = null
         plugins.Auth.updateHeaders()
+        delete plugins.Auth
+
+      if plugins.Permissions?
+        plugins.Permissions.setUser(null)
+        # XXX: Temporary workaround until Annotator v2.0 or v1.2.10
+        plugins.Permissions.options.permissions =
+          read: []
+          update: []
+          delete: []
+          admin: []
 
-      plugins.Permissions.setUser(null)
-      # XXX: Temporary workaround until the fixed version upstream annotator is consumed
-      # The problem is that the permissions plugin, when setting the annotation.permissions property
-      # does not copy its options.permissions object, so modifying the annotation.permissions object
-      # modifes the plugin's options.permissions object too. After that this can be removed.
-      plugins.Permissions.options.permissions =
-        read: []
-        update: []
-        delete: []
-        admin: []
       if newValue?
-        if not plugins.Auth?
-          annotator.addPlugin 'Auth', token: newValue
-        else
-          plugins.Auth.setToken(newValue)
+        acct = "acct:#{newValue.username}@#{newValue.provider}"
+        annotator.addPlugin 'Auth',
+          tokenUrl: "/api/token?persona=#{acct}"
+
         plugins.Auth.withToken (token) =>
           plugins.Permissions._setAuthFromToken token
 
@@ -75,8 +73,9 @@ class App
             annotator.setTool 'highlight'
           else
             $scope.reloadAnnotations()
-      else
-        delete plugins.Auth
+      else if oldValue?
+        authentication.$logout => $scope.$broadcast '$reset'
+
         if annotator.tool isnt 'comment'
           annotator.setTool 'comment'
         else