Allow adding items from different servers to playlist

[JonnyWong16]

Description

Allow adding items from different servers to playlist.

Playlist.addItems(items) automatically splits the items into separate API calls since Plex only allows adding items from one server at a time. This will keep the items in the order they added in the list.

Closes#1409

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the docstring for new or existing methods
• I have added tests when applicable

[glensc]

This assumes all items to be added have _server initialized to the actual server. This means if you load a playlist with remote items from local server and try to save, it will save with wrong server id, resulting data loss as invalid ids will be ignored.

...should somehow use sourceURI if present

[glensc]

I currently put together something like this. this is able to take existing playlist (via server.playlist() call) and save it.

defaddItems(self, items):
""" Add items to the playlist. Parameters: items (List): List of :class:`~plexapi.audio.Audio`, :class:`~plexapi.video.Video`, or :class:`~plexapi.photo.Photo` objects to be added to the playlist. Raises: :class:`plexapi.exceptions.BadRequest`: When trying to add items to a smart playlist. """ifself.smart:
raiseBadRequest('Cannot add items to a smart playlist.')
ifitemsandnotisinstance(items, (list, tuple)):
items= [items]
# Group items by server to maintain order when adding items from multiple servers# for server, _items in groupby(items, key=lambda item: item._server):forsourceURI, _itemsingroupby(items, key=lambdaitem: item.sourceURI):
ratingKeys= []
foritemin_items:
ifitem.listType!=self.playlistType: # pragma: no coverraiseBadRequest(f'Can not mix media types when building a playlist: 'f'{self.playlistType} and {item.listType}')
sourceURI=item._server._uriRoot() ifsourceURIisNoneelsesourceURIratingKeys.append(str(item.ratingKey))
ratingKeys=','.join(ratingKeys)
# uri = f'{server._uriRoot()}/library/metadata/{ratingKeys}'uri=f'{sourceURI}/library/metadata/{ratingKeys}'args= {'uri': uri}
key=f"{self.key}/items{utils.joinArgs(args)}"self._server.query(key, method=self._server._session.put)
returnself