message: Refactor expand var in course container
diff: <app-badge [displayNumber]="courses.length"></app-badge>
  - <button class="open-toggle" [class.opened]="expand == true" mat-icon-button>
  + <button class="open-toggle" [class.opened]="expand" mat-icon-button>
  <mat-icon>arrow_drop_down</mat-icon>
  </button></div>
  -<div class="courses" *ngIf="expand == true">
  +<div class="courses" *ngIf="expand">
  <p *ngIf="!courses.length">No courses added yet.</p>
  <app-course *ngFor="let course of courses" [course]="course" (onEnroll)="enrollCallback($event)"></app-course>
  </div>
  