Add playlists API service endpoint

[dennis531]

The added Playlist API Endpoint is based on the opencast pull request with the playlists.

[ferishili]

Hi @dennis531,
thank you very much for your contribution, would you mind adding the whole documentation to the GitHub wiki as well?
Please take a look at the /api/** endpoints here: https://github.com/elan-ev/opencast-php-library/wiki/API-Endpoints

[ferishili]

The Unit tests are failing, I would assume that is because of the version increment to 1.11.0 which is not yet provided by stable.opencast.org, therefore we need to make sure that version is only changed to 1.11.0 inside the OcPlaylistsApiTest and handle the checkers and exceptions there!

[dennis531]

After the OC pull request is merged, I will add the wiki entry and implement the version handling in the tests. Perhaps the API could still change.

[dennis531]

Now the playlist test checks if the configured opencast has support for the playlists api. If not supported, the tests will be skipped.

[dennis531]

The playlists api is documented at https://github.com/elan-ev/opencast-php-library/wiki/OcPlaylistsApi.

[dennis531]

@ferishili you have to add the library version in https://github.com/elan-ev/opencast-php-library/wiki/OcPlaylistsApi#version when you create a new library version.

Edit: I added version 1.6

[ferishili]

Hi @dennis531
Thank you very much for your contribution.
Everything looks good