message: Check if form is valid before submit
diff: <div class="center-both">
  <h1>Create Course</h1>
  <mat-card>
  - <form class="course-form" (ngSubmit)="createCourse()" [formGroup]="newCourse">
  + <form class="course-form" (ngSubmit)="newCourse.valid && createCourse()" [formGroup]="newCourse">
  <mat-form-field class="full-width">
  <input matInput formControlName="name" placeholder="Course Name">
  <div *ngIf="nameError">
  