Add support for playlists, the watch later feed, multiple users, and subscribed channels

[ayaadev]

Description

This PR aims to add the following features:

• Ability to browse the "Watch Later" playlist, and other user playlists, achieved by:
  • Storing usernames in the data file
  • Creating a new playlists_menu function for non-watch later playlists.
  • Adding logic in the list_videos function to get the watch later playlist ID and pass it to the get_videos function. This bypasses the cache and ensures users get the correct results when they change accounts.
  • Adding two new strings in the base translations file.
  • Updating the README.md to say that the username is now stored to make loading the playlists faster.
• Multiple user functionality
• Display subscribed channels alongside videos from the subscription feed

These features will close three issues, therefore they are in development.

As of now, this PR is a draft and only achieves the first feature (user playlists).

Related issues

• Browse user playlists #13
• Allow multiple users #14
• Add menu item for list of subscribed channels #15

Has this been tested?

• 👍 Yes, I have done the following tests:
  • The first feature (user playlists) has been tested:
    • The user is prompted to login again after the upgrade, preventing a KeyError.
    • The cached results are reset if a user changes accounts.
    • No errors are given when using the feature.
    • The correct error is given when there are no videos in the playlist.

Screenshots

The new "Watch Later" and "Playlists" menu items.

The playlist view.