Add support for temp usernames and an interstitial to confirm username

When a user now logs in for the first time for any external auth (LDAP, JWT, Keystone, Github, Google, Dex), they will be presented with a confirmation screen that affords them the opportunity to change their Quay-assigned username.

Addresses most of the user issues around #74

static/js/directives/ui/namespace-input.js

@@ -11,13 +11,14 @@ angular.module('quay').directive('namespaceInput', function () {
     scope: {
       'binding': '=binding',
       'isBackIncompat': '=isBackIncompat',
+      'hasExternalError': '=?hasExternalError',
+
       'namespaceTitle': '@namespaceTitle',
     },
     controller: function($scope, $element) {
       $scope.USERNAME_PATTERN = USERNAME_PATTERN;
       $scope.usernamePattern = new RegExp(USERNAME_PATTERN);
 
-
       $scope.$watch('binding', function(binding) {
         if (!binding) {
           $scope.isBackIncompat = false;