feat(login): add login authentication and authorization (#122)

Add login basic authentication, oauth2 authentication, two factor
authentication and authorization and allow to reset password on expiry.

Fixes #117, #118, #119, #120

src/app/core/alert.service.ts

@@ -0,0 +1,18 @@
+import { Injectable, EventEmitter } from '@angular/core';
+
+@Injectable({
+  providedIn: 'root'
+})
+export class AlertService {
+
+  public alertEvent: EventEmitter<any>;
+
+  constructor() {
+    this.alertEvent = new EventEmitter();
+  }
+
+  alert(alertEvent: any) {
+    this.alertEvent.emit(alertEvent);
+  }
+
+}