Make emails unique

Emails are made unique. When user attempts to sign in through a provider in which his email is one that is already registered, user is redirected to the signin page with an error passed as a query string parameter.

modules/users/client/config/users.client.routes.js

@@ -36,7 +36,7 @@ angular.module('users').config(['$stateProvider',
 				templateUrl: 'modules/users/views/authentication/signup.client.view.html'
 			}).
 			state('authentication.signin', {
-				url: '/signin',
+				url: '/signin?err',
 				templateUrl: 'modules/users/views/authentication/signin.client.view.html'
 			}).
 			state('password', {

modules/users/client/controllers/authentication.client.controller.js

@@ -4,6 +4,9 @@ angular.module('users').controller('AuthenticationController', ['$scope', '$http
 	function($scope, $http, $location, Authentication) {
 		$scope.authentication = Authentication;
 
+		// Get an eventual error defined in the URL query string:
+		$scope.error = $location.search().err;
+
 		// If user is signed in then redirect back home
 		if ($scope.authentication.user) $location.path('/');
 

modules/users/client/views/authentication/signin.client.view.html

@@ -18,12 +18,12 @@
 					  or 
 					<a data-ui-sref="authentication.signup">Sign up</a>
 				</div>
-				<div class="forgot-password">
+				<div class="text-center forgot-password">
 					<a data-ui-sref="password.forgot">Forgot your password?</a>
 				</div>
-				<div data-ng-show="error" class="text-center text-danger">
-					<strong data-ng-bind="error"></strong>
-				</div>
+				<alert type="danger" data-ng-show="error" class="text-center text-danger">
+					<span data-ng-bind="error"></span>
+				</alert>
 			</fieldset>
 		</form>
 	</div>