https://stackoverflow.com/questions/34323480/in-angular-how-do-you-determine-the-active-route
<!-- if multiple classes need to be inserted -->
<a [routerLink]="['/home']" [routerLinkActive]="['is-active']">Home</a>
<a [routerLink]="['/home']" [routerLinkActive]="'is-active'">Home</a>
<a [routerLink]="['/home']" routerLinkActive="is-active">Home</a>