Move language switch to header component

src/app/app.component.ts

 import { Component } from '@angular/core';
-import { TranslateService } from '@ngx-translate/core';
 
 @Component({
   selector: 'app-root',
@@ -8,9 +7,4 @@ import { TranslateService } from '@ngx-translate/core';
 })
 export class AppComponent {
   title = 'ARSnova';
-
-  constructor(private translateService: TranslateService) {
-    translateService.setDefaultLang('en');
-  }
-
 }

src/app/components/fragments/header/header.component.html

@@ -5,10 +5,20 @@
     </button>
     <span class="app-title" (click)="goToHomepage()">ARSnova</span>
     <span class="fill-remaining-space"></span>
+
+    <mat-menu #langMenu="matMenu">
+      <button mat-menu-item (click)="useLanguage('de')">{{ 'header.german' | translate }}</button>
+      <button mat-menu-item (click)="useLanguage('en')">{{ 'header.english' | translate }}</button>
+    </mat-menu>
+
+    <button mat-icon-button [matMenuTriggerFor]="langMenu">
+      <mat-icon>language</mat-icon>
+    </button>
+
     <mat-menu #appMenu="matMenu" [overlapTrigger]="false">
       <button mat-menu-item (click)="logout()">
         <mat-icon>exit_to_app</mat-icon>
-        <span>Logout</span>
+        <span>{{ 'header.logout' | translate }}</span>
       </button>
     </mat-menu>
     <button *ngIf="user" mat-button [matMenuTriggerFor]="appMenu">

src/app/components/fragments/header/header.component.ts

@@ -5,6 +5,7 @@ import { Router } from '@angular/router';
 import { User } from '../../../models/user';
 import { UserRole } from '../../../models/user-roles.enum';
 import { Location } from '@angular/common';
+import { TranslateService } from '@ngx-translate/core';
 
 @Component({
   selector: 'app-header',
@@ -17,7 +18,8 @@ export class HeaderComponent implements OnInit {
   constructor(public location: Location,
               private authenticationService: AuthenticationService,
               private notification: NotificationService,
-              public router: Router) {
+              public router: Router,
+              private translationService: TranslateService) {
   }
 
   ngOnInit() {
@@ -51,4 +53,8 @@ export class HeaderComponent implements OnInit {
     }
     this.router.navigate([route]);
   }
+
+  useLanguage(language: string) {
+    this.translationService.use(language);
+  }
 }