113319: Add dropdown entry to clear selection

(cherry picked from commit 13d1547b3dbf5d4cd74617d6327044da798ed44e)

Author: AAwouters

src/app/shared/form/builder/ds-dynamic-form-ui/models/scrollable-dropdown/dynamic-scrollable-dropdown.component.html

@@ -41,6 +41,12 @@
          [scrollWindow]="false">
 
       <button class="dropdown-item disabled" *ngIf="optionsList && optionsList.length === 0">{{'form.no-results' | translate}}</button>
+      <button class="dropdown-item collection-item text-truncate"
+              (click)="onSelect(undefined); sdRef.close()" (mousedown)="onSelect(undefined); sdRef.close()"
+              title="{{ 'dropdown.clear.tooltip' | translate }}" role="option"
+      >
+        <i>{{ 'dropdown.clear' | translate }}</i>
+      </button>
       <button class="dropdown-item collection-item text-truncate" *ngFor="let listEntry of optionsList; let i = index"
               [class.active]="i === selectedIndex"
               (keydown.enter)="onSelect(listEntry); sdRef.close()" (mousedown)="onSelect(listEntry); sdRef.close()"

src/assets/i18n/en.json5

@@ -1678,6 +1678,10 @@
 
   "deny-request-copy.success": "Successfully denied item request",
 
+  "dropdown.clear": "Clear selection",
+
+  "dropdown.clear.tooltip": "Clear the selected option",
+
   "dso.name.untitled": "Untitled",
 
   "dso.name.unnamed": "Unnamed",