message: removes merge duplicate
diff: <button mat-menu-item *ngIf="isLoggedIn() && isAdmin()" routerLink="/admin" routerLinkActive="active">
  <mat-icon>settings</mat-icon>
  <span>{{ 'mainMenu.admin' | translate }}</span>
  - <span>Admin</span>
  </button>
  <button mat-menu-item *ngIf="isLoggedIn() && isStudent()" routerLink="/userSettings" routerLinkActive="active">
  <mat-icon>settings</mat-icon>
  