Prevent an admin from deleting their own account

Backport of the UFAL self-delete guard from dtq-dev (dspace-angular
#1335, #1357, #1373) to this customer branch. The EPeople registry and
the EPerson form now hide/disable the delete action for the currently
authenticated user (with an explanatory tooltip), show a contextual
warning in the confirmation modal when the target is a submitter and/or
an administrator, and surface a friendly notification when the backend
rejects a self-delete.

Shared logic lives in the new EPersonDeleteGuardService so both call
sites stay in sync.

Refs dataquest-dev/dspace-customers#855

Author: Matus Kasak

src/app/access-control/epeople-registry/epeople-registry.component.spec.ts

@@ -283,9 +283,8 @@ describe('EPeopleRegistryComponent', () => {
       const deleteButtons = fixture.debugElement.queryAll(By.css('.access-control-deleteEPersonButton'));
 
       expect(deleteButtons.length).toBe(2);
-      expect(deleteButtons[0].nativeElement.getAttribute('aria-disabled')).toBeNull();
-      expect(deleteButtons[1].nativeElement.getAttribute('aria-disabled')).toBe('true');
-      expect(deleteButtons[1].nativeElement.classList.contains('disabled')).toBeTrue();
+      expect(deleteButtons[0].nativeElement.disabled).toBeFalse();
+      expect(deleteButtons[1].nativeElement.disabled).toBeTrue();
     });
 
     it('should call submitter checks and compose the combined warning label', fakeAsync(() => {

src/app/access-control/epeople-registry/eperson-form/eperson-form.component.spec.ts

@@ -37,7 +37,6 @@ import { FollowLinkConfig } from '../../../shared/utils/follow-link-config.model
 import { ActivatedRoute, Router } from '@angular/router';
 import { RouterStub } from '../../../shared/testing/router.stub';
 import { ActivatedRouteStub } from '../../../shared/testing/active-router.stub';
-import { RouterTestingModule } from '@angular/router/testing';
 import { WorkspaceitemDataService } from '../../../core/submission/workspaceitem-data.service';
 import { WorkflowItemDataService } from '../../../core/submission/workflowitem-data.service';
 import { SearchService } from '../../../core/shared/search/search.service';
@@ -664,8 +663,7 @@ describe('EPersonFormComponent', () => {
     it('should render the delete button as disabled for the current user', () => {
       const deleteButton = fixture.debugElement.query(By.css('.delete-button'));
       expect(deleteButton).not.toBeNull();
-      expect(deleteButton.nativeElement.getAttribute('aria-disabled')).toBe('true');
-      expect(deleteButton.nativeElement.classList.contains('disabled')).toBeTrue();
+      expect(deleteButton.nativeElement.disabled).toBeTrue();
     });
   });