Resolve "Session ID input field enhancement"

Closes #197 (closed)

src/app/components/shared/room-join/room-join.component.html

@@ -8,7 +8,7 @@
                         placeholder="Session-Id" [formControl]="roomFormControl" [errorStateMatcher]="matcher"/>
       <mat-hint align="end">{{ roomId.value.length - (roomId.value.split(' ').length -1) }} / 8</mat-hint>
       <mat-error *ngIf="roomFormControl.hasError('required')">{{ 'home-page.please-enter' | translate}}</mat-error>
-      <mat-error *ngIf="roomFormControl.hasError('minlength')">{{ 'home-page.exactly-8' | translate}}</mat-error>
+      <mat-error *ngIf="roomFormControl.hasError('pattern')">{{ 'home-page.only-numbers' | translate}}</mat-error>
     </mat-form-field>
     <button mat-fab color="accent" type="submit">
       <mat-icon>input</mat-icon>