MDL-49059 medialib: Add tests for Youtube videos within playlists
MDL-49059 medialib: Add tests for Youtube videos within playlists

As well as embedding playlists, you can embed specific videos from them -
resulting in the playlist UI displaying, but starting with the specified
video rather than the first in the playlist.  These URLs should be covered
by the tests to ensure that we're handling them properly.

dilawar/moodle