[BUG] Add To Watchlist Failure Caused by Plex Updating Base URL Metadata Endpoint

[Sebastrn]

I'm referencing some PR and issues from other repos here:

pushingkarmaorg/python-plexapi#1541
pushingkarmaorg/python-plexapi#1542

Kometa-Team/Kometa#2745
rivenmedia/riven#1134

I believe the metadata.provider.plex.tv is referenced in this repo and should be updated to discover.provider.plex.tv.
You also reference user.watchlist() which plexapi would need to update and push as a new version.

[treysu]

I am assuming that the plexapi team is working on a fix for this, or will be soon. Unfortunately, the likely best option will be to wait for them to resolve the issue and update my script to use the newest version of their library.

I will keep tabs on the issue and brainstorm to see if there is a simple fix on my end in the meantime.

Unclear if the metadata endpoint as a whole has changed, or just the portion interacting with the watchlist. I will investigate that as well.

[treysu]

Resolved #17