Story

After RHIDP-5471 is implemented, we should ensure that with playwright tests and a custom header test plugin.

Acceptance Criteria

This story should focus on the application.header mount point and optional on the extendability features of the global header while RHIDP-5474 should focus on the features with the default header.

1. Test if a 2nd header can be installed
2. Test if an extra button can be added to the default global header.

The global-header-test plugin should be used for this.