Add internet_service to SpotifySearchProvider so custom context menu is correctly shown on playlist items created from the global search
Also add internet_service method for other search providers which have a internet services.
Shouldn't change anything in practice, but better to have items correctly inserted as Internet items FWIW. And will avoid other "custom context menu not working" issues if one day we implement one for
these services.
Add Spotify tracks to Spotify playlists by drag and drop