Content projection with selectors in themed components is not working

[AndreaBarbasso]

Describe the bug

Angular's content projection with selectors (e.g. <ng-content select="[additionalSearchOptions]") in themed components is not working properly. Instead of projecting different elements in different content outlets, it projects all of them into the last (or default) ng-content found.

To Reproduce

Steps to reproduce the behavior:

1. Use content projection in a themed component, for example you can use this template into the my-dspace-page component:

  <ds-search
    [configuration]="configuration"
    [configurationList]="(configurationList$ | async)"
    [context]="context"
    [viewModeList]="viewModeList">
      <p additionalSearchOptions>additionalSearchOptions</p>
      <p searchContentTop>searchContentTop</p>
  </ds-search>

2. You will see that all the content will be projected in the same ng-content outlet, i.e. the last ng-content child of the ds-search component.

Expected behavior

Each element should be projected in the correct ng-content outlet.