fix(datepicker): prevent auto open of datepicker slave

The datepicker slave automatically opens its toggle on multiple triggers.
For some circumstances this is annoying for the user. This change allows
to configure the slave via an input to prevent this behaviour.

closes sbb-design-systems#36

projects/sbb-esta/angular-public/src/lib/datepicker/datepicker/datepicker.component.ts

@@ -125,6 +125,12 @@ export class DatepickerComponent<D> implements OnDestroy {
 
   master: DatepickerComponent<D> | null;
 
+  /**
+   * If set to <code>true</code> (default: <code>false</code>) on a slave instance,
+   * it will not open the date picker automatically
+   */
+  @Input() preventAutoOpen = false;
+
   @HostBinding('class.sbb-datepicker') cssClass = true;
 
   /**
@@ -327,7 +333,8 @@ export class DatepickerComponent<D> implements OnDestroy {
           v => !!this.slave.selected && this._dateAdapter.compareDate(v, this.slave.selected) > 0
         ),
         tap(r => (r ? (this.slave.datepickerInput.value = null) : undefined)),
-        filter(() => !this.slave.datepickerInput.value)
+        filter(() => !this.slave.datepickerInput.value),
+        filter(() => !this.preventAutoOpen)
       )
       .subscribe(() => this.slave.open());
   }