LIBDRUM-902. Fixed "Delete ETD Department" button display on create form

Modified the check for displaying the "Delete ETD Department" button to
take into account whether the department exists.

Also simplified the "translateService" call by removing an
"observableCombineLatest" operator that only had one argument, and
fixed a deprecation warning on a second "observerCombineLatest" operator
by converting the arguments to an array.

https://umd-dit.atlassian.net/browse/LIBDRUM-902

src/app/etdunit-registry/etdunit-form/etdunit-form.component.ts

@@ -34,6 +34,8 @@ import {
 } from 'rxjs';
 import {
   debounceTime,
+  map,
+  switchMap,
   take,
 } from 'rxjs/operators';
 import { DSONameService } from 'src/app/core/breadcrumbs/dso-name.service';
@@ -52,6 +54,7 @@ import { AlertType } from 'src/app/shared/alert/alert-type';
 import { ConfirmationModalComponent } from 'src/app/shared/confirmation-modal/confirmation-modal.component';
 import {
   hasValue,
+  hasValueOperator,
   isNotEmpty,
 } from 'src/app/shared/empty.util';
 import { FormBuilderService } from 'src/app/shared/form/builder/form-builder.service';
@@ -170,8 +173,15 @@ export class EtdUnitFormComponent implements OnInit, OnDestroy {
         this.setActiveEtdUnit(params.etdunitId);
       }
     }));
-    this.canEdit$ = this.authorizationService.isAuthorized(FeatureID.AdministratorOf);
-    observableCombineLatest(this.translateService.get(`${this.messagePrefix}.etdunitName`)).subscribe(([etdunitNameLabel]) => {
+    this.canEdit$ = this.etdunitDataService.getActiveEtdUnit().pipe(
+      hasValueOperator(),
+      switchMap((etdUnit: EtdUnit) => {
+        return this.authorizationService.isAuthorized(FeatureID.CanDelete, isNotEmpty(etdUnit) ? etdUnit.self : undefined).pipe(
+          map((isAuthorized: boolean) => isAuthorized),
+        );
+      }),
+    );
+    this.translateService.get(`${this.messagePrefix}.etdunitName`).subscribe((etdunitNameLabel) => {
       this.etdunitName = new DynamicInputModel({
         id: 'etdunitName',
         label: etdunitNameLabel,
@@ -194,10 +204,10 @@ export class EtdUnitFormComponent implements OnInit, OnDestroy {
       }
 
       this.subs.push(
-        observableCombineLatest(
+        observableCombineLatest([
           this.etdunitDataService.getActiveEtdUnit(),
           this.canEdit$,
-        ).subscribe(([activeEtdUnit, canEdit]) => {
+        ]).subscribe(([activeEtdUnit, canEdit]) => {
           if (activeEtdUnit != null) {
             // Disable etdunit name exists validator
             this.formGroup.controls.etdunitName.clearAsyncValidators();