allow custom auth endpoint (#1294)

src/components/App/App.js

@@ -84,6 +84,7 @@ class App extends React.Component {
             isFetching: auth && auth.get('isFetching'),
             siteId: this.props.config.getIn(["backend", "site_domain"]),
             base_url: this.props.config.getIn(["backend", "base_url"], null),
+            authEndpoint: this.props.config.getIn(["backend", "auth_endpoint"]),
             config: this.props.config,
           })
         }