HTML
<mat-card class="example-card">
<mat-card-header>
<mat-card-title>Register</mat-card-title>
</mat-card-header>
<mat-card-content>
<form class="example-form">
<table class="example-full-width" cellspacing="0">
<tr>
<td>
<mat-form-field class="example-full-width">
<input matInput placeholder="UserName" [(ngModel)]="username" name="username" required>
</mat-form-field>
</td>
</tr>
</table>
</form>
<mat-spinner [style.display]="showSpinner ? 'block' : 'none'"></mat-spinner>
</mat-card-content>
<mat-card-actions>
<button mat-raised-button (click)="register()" color="primary">Register</button>
</mat-card-actions>
</mat-card>
