Allow Milestones to be moved to the drop zone as their date can be changed although their duration can't

frontend/src/app/features/calendar/op-calendar.service.ts

@@ -243,10 +243,14 @@ export class OpCalendarService extends UntilDestroyedMixin {
     return this.urlParams.cview as string|undefined;
   }
 
-  public eventDurationEditable(wp:WorkPackageResource):boolean {
+  dateEditable(wp:WorkPackageResource):boolean {
     const schema = this.schemaCache.of(wp);
     const schemaEditable = schema.isAttributeEditable('startDate') && schema.isAttributeEditable('dueDate');
-    return (wp.isLeaf || wp.scheduleManually) && schemaEditable && !this.isMilestone(wp);
+    return (wp.isLeaf || wp.scheduleManually) && schemaEditable;
+  }
+
+  eventDurationEditable(wp:WorkPackageResource):boolean {
+    return this.dateEditable(wp) && !this.isMilestone(wp);
   }
 
   /**

frontend/src/app/features/team-planner/team-planner/planner/team-planner.component.html

@@ -138,11 +138,11 @@
           [class.op-team-planner--remove-dropzone_active]="dropzone.isHovering && dropzone.canDrop"
           [class.op-team-planner--remove-dropzone_forbidden]="!dropzone.canDrop"
         >
-      <span
-        *ngIf="dropzone.canDrop"
-        class="op-team-planner--dropzone-label"
-        [textContent]="text.drag_here_to_remove"
-      ></span>
+          <span
+            *ngIf="dropzone.canDrop"
+            class="op-team-planner--dropzone-label"
+            [textContent]="text.drag_here_to_remove"
+          ></span>
           <span
             *ngIf="!dropzone.canDrop"
             class="op-team-planner--dropzone-label"

frontend/src/app/features/team-planner/team-planner/planner/team-planner.component.ts

@@ -122,13 +122,17 @@ export class TeamPlannerComponent extends UntilDestroyedMixin implements OnInit,
       filter((dragging) => !!dragging),
       map((dragging) => {
         const workPackage = (dragging as EventDragStartArg).event.extendedProps.workPackage as WorkPackageResource;
-        const durationEditable = this.calendar.eventDurationEditable(workPackage);
+        const dateEditable = this.calendar.dateEditable(workPackage);
         const resourceEditable = this.eventResourceEditable(workPackage);
-        return durationEditable && resourceEditable;
+        return dateEditable && resourceEditable;
       }),
     );
 
-  dropzone$ = combineLatest([this.draggingItem$, this.dropzoneHovered$, this.dropzoneAllowed$])
+  dropzone$ = combineLatest([
+    this.draggingItem$,
+    this.dropzoneHovered$,
+    this.dropzoneAllowed$,
+  ])
     .pipe(
       map(([dragging, isHovering, canDrop]) => ({ dragging, isHovering, canDrop })),
     );