<mat-toolbar color="accent" class="toolbar">
  <span>{{ username }}</span>

  <button mat-button (click)="logout()" *ngIf="isLoggedIn">Logout</button>
  <button mat-button (click)="login()" *ngIf="!isLoggedIn">Login</button>
</mat-toolbar>
<div class="content_container">
  <router-outlet></router-outlet>
</div>