feat(core(js)): improve Google Authenticator on login page, add QR code

Closes #2722

UI/WebServerResources/js/Common/sgQrCode.directive.js

@@ -0,0 +1,41 @@
+/* -*- Mode: javascript; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+
+(function() {
+  /* jshint validthis: true, newcap: false */
+  'use strict';
+
+  /**
+   * sgQrCode - Build a otpauth URI and generate a QR Code for the provided secret.
+   * @see {@link https://davidshimjs.github.io/qrcodejs/|QRCode.js}
+   * @memberof SOGo.Common
+   * @example:
+     <sg-qr-code text="secret"/>
+  */
+  sgQrCode.$inject = ['sgSettings'];
+  function sgQrCode(Settings) {
+    return {
+      restrict: 'E',
+      scope: {
+        text: '@',
+        width: '@',
+        height: '@'
+      },
+      link: link
+    };
+
+    function link(scope, element, attrs) {
+      var width = parseInt(scope.width) || 256,
+          height = parseInt(scope.height) || width,
+          uri = 'otpauth://totp/SOGo:' + Settings.activeUser('email') + '?secret=' + scope.text.replace(/=+$/, '') + '&issuer=SOGo';
+      new QRCode(element[0], {
+        text: uri,
+        width: width,
+        height: height
+      });
+    }
+  }
+
+  angular
+    .module('SOGo.Common')
+    .directive('sgQrCode', sgQrCode);
+})();