[bug] <rh-accordion> is not responding to expanded-index or manually setting expanded attribute on headers

[zeroedin]

Reported by Alistair McGranaghan

this test code is not working for me:

<rh-accordion expanded-index="1" large="true">
  <rh-accordion-header>test title</rh-accordion-header>
  <rh-accordion-panel>
    <p>Test content</p>
  </rh-accordion-panel>
  <rh-accordion-header>test title 2</rh-accordion-header>
  <rh-accordion-panel>
    <p>Test content 2</p>
  </rh-accordion-panel>
</rh-accordion>

The initially expanded demo seems to work on ux.redhat.com

However if you try and to set expanded-index on the <rh-accordion> it does not respond. Here is a Codepen reproduction: https://codepen.io/zeroedin/pen/eYqrBxJ where I am setting expanded-index on the first example and expanded attributes on headers manually and programmatically in the second.

Alistair also mentioned that adding expanded on headers for him was not working in Shared Libs but I wasn't able to reproduce.

[zeroedin]

Given shared_libs use I asked @zhawkins to run a test for me and he was not able to reproduce the expanded attribute issue using the following snippet:

<rh-accordion large="true">
  <rh-accordion-header>test title</rh-accordion-header>
  <rh-accordion-panel>
    <p>Test content</p>
  </rh-accordion-panel>
  <rh-accordion-header expanded>test title 2</rh-accordion-header>
  <rh-accordion-panel>
    <p>Test content 2</p>
  </rh-accordion-panel>
</rh-accordion>

Worked on his test environment:

[markcaron]

@zeroedin can we ensure the spec.ts catches this expanded feature?

[zeroedin]

@markcaron https://github.com/patternfly/patternfly-elements/blob/96379988019be51ea4bce6146a9121c51c898a2b/elements/pf-accordion/test/pf-accordion.spec.ts#L226-L245

So we are testing for this in pf-accordion so we'd bring these tests over (as they apply) and add to them if needed. My thoughts are because we removed the direct relation to BaseAccordion we no longer had the tie in to the tests.