fix(signpost): set aria-expanded on button during initial render (bac…

…kport to main) (#1220)

Backport 6717669 from #1213. <br> ## PR
Checklist

Please check if your PR fulfills the following requirements:

- [x] Tests for the changes have been added (for bug fixes / features)
- [ ] Docs have been added / updated (for bug fixes / features)
- [ ] If applicable, have a visual design approval

## PR Type

What kind of change does this PR introduce?

&lt;!-- Please check the one that applies to this PR using
&quot;x&quot;. --&gt;

- [x] Bugfix
- [ ] Feature
- [ ] Code style update (formatting, local variables)
- [ ] Refactoring (no functional changes, no api changes)
- [ ] Build related changes
- [ ] CI related changes
- [ ] Documentation content changes
- [ ] Other... Please describe:

## What is the current behavior?

The initial signpost trigger button is rendered without the
aria-expanded attribute, which is necessary for screen readers to
identify the button as having an expanded state.

Issue Number: CDE-1632

## What is the new behavior?
The initial render of the trigger button has the
aria-expanded=&quot;false&quot; attribute/value.

## Does this PR introduce a breaking change?

- [ ] Yes
- [X] No

&lt;!-- If this PR contains a breaking change, please describe the
impact and migration path for existing applications below. --&gt;

## Other information

Co-authored-by: Will Ernest <[email protected]>

projects/angular/src/popover/signpost/signpost-trigger.spec.ts

@@ -70,7 +70,7 @@ export default function (): void {
     });
 
     it('reflects the correct aria-expanded state', () => {
-      expect(trigger.getAttribute('aria-expanded')).toBeFalsy();
+      expect(trigger.getAttribute('aria-expanded')).toBe('false');
       trigger.click();
       fixture.detectChanges();
       expect(trigger.getAttribute('aria-expanded')).toBe('true');

projects/angular/src/popover/signpost/signpost-trigger.ts

@@ -30,7 +30,7 @@ import { SignpostIdService } from './providers/signpost-id.service';
  *
  */
 export class ClrSignpostTrigger implements OnDestroy {
-  ariaExpanded: boolean;
+  ariaExpanded = false;
   ariaControl: string;
   isOpen: boolean;