ROENROLL-1517 inline message when searching for invalid subject

src/app/degree-planner/course-search/course-search.component.html

@@ -17,6 +17,10 @@
   </mat-form-field>
 
   <mat-form-field class="example-full-width">
+    <mat-hint align="end" *ngIf="courseSearchForm?.get('subject')?.invalid">
+      Please select an existing subject or &lsquo;All&rsquo;
+    </mat-hint>
+
     <input
       type="text"
       placeholder="Subject"

src/app/degree-planner/course-search/course-search.component.ts

@@ -200,9 +200,7 @@ export class CourseSearchComponent implements OnInit, OnDestroy {
     const subjectCode = this.getSubjectCode(subject);
 
     if (!subjectCode) {
-      this.snackBar.open('Please select a valid subject', undefined, {
-        duration: 6000,
-      });
+      this.courseSearchForm.controls['subject'].setErrors({ invalid: true });
       return;
     }