Add ancestors filter to show only relevant subprojects in "only subprojects" and "including subprojects" filter

frontend/src/app/features/work-packages/components/filters/filter-project/filter-project.component.html

@@ -9,5 +9,6 @@
     [id]="'values-' + filter.id"
     class="advanced-filters--ng-select -multi-select"
     (valueChange)="onChange($event)"
+    [apiFilters]="additionalProjectApiFilters"
   ></op-project-autocompleter>
 </div>

frontend/src/app/features/work-packages/components/filters/filter-project/filter-project.component.ts

@@ -30,6 +30,7 @@ import {
   ChangeDetectionStrategy,
   Component,
   Input,
+  OnInit,
   Output,
 } from '@angular/core';
 import { I18nService } from 'core-app/core/i18n/i18n.service';
@@ -40,26 +41,38 @@ import { componentDestroyed } from '@w11k/ngx-componentdestroyed';
 import { QueryFilterInstanceResource } from 'core-app/features/hal/resources/query-filter-instance-resource';
 import { IProjectAutocompleteItem } from 'core-app/shared/components/autocompleter/project-autocompleter/project-autocomplete-item';
 import { ApiV3Service } from 'core-app/core/apiv3/api-v3.service';
+import { ApiV3ListFilter } from 'core-app/core/apiv3/paths/apiv3-list-resource.interface';
+import { CurrentProjectService } from 'core-app/core/current-project/current-project.service';
 
 @Component({
   selector: 'op-filter-project',
   templateUrl: './filter-project.component.html',
   changeDetection: ChangeDetectionStrategy.OnPush,
 })
-export class FilterProjectComponent extends UntilDestroyedMixin {
+export class FilterProjectComponent extends UntilDestroyedMixin implements OnInit {
   @Input() public shouldFocus = false;
 
   @Input() public filter:QueryFilterInstanceResource;
 
   @Output() public filterChanged = new DebouncedEventEmitter<QueryFilterInstanceResource>(componentDestroyed(this));
 
+  additionalProjectApiFilters:ApiV3ListFilter[] = [];
+
   constructor(
     readonly I18n:I18nService,
     readonly apiV3Service:ApiV3Service,
+    readonly currentProjectService:CurrentProjectService,
   ) {
     super();
   }
 
+  ngOnInit():void {
+    const projectID = this.currentProjectService.id;
+    if (projectID && (this.filter.id === 'subprojectId' || this.filter.id === 'onlySubproject')) {
+      this.additionalProjectApiFilters.push(['ancestor', '=', [projectID]]);
+    }
+  }
+
   async onChange(val:HalResource[]|IProjectAutocompleteItem[]):Promise<void> {
     if (val === this.filter.values || val === undefined) {
       return;