message: added docs on proper function call for db mutator
diff: @@ -493,7 +493,7 @@ DASHBOARD_TEMPLATE_ID = None
  # username. The function receives the connection uri object, connection
  # params, the username, and returns the mutated uri and params objects.
  # Example:
  -# def DB_CONNECTION_MUTATOR(uri, params, username, security_manager):
  +# def DB_CONNECTION_MUTATOR(uri, params, username, security_manager, source):
  # user = security_manager.find_user(username=username)
  # if user and user.email:
  # uri.username = user.email
  