Add support for Square Art

[JonnyWong16]

Description

Add support for Square Art.

Ref.: https://forums.plex.tv/t/plex-media-server/30447/693

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

[Copilot]

Pull Request Overview

This PR adds support for Square Art images in PlexAPI, extending the existing image handling capabilities (art, poster, theme) to include a new square art type. This aligns with Plex Media Server's support for square artwork as referenced in the Plex forums.

Key changes:

• Implements SquareArtMixin, SquareArtUrlMixin, and SquareArtLockMixin classes with full CRUD operations for square art
• Adds SquareArt media resource class and registers the squareArt tag type
• Integrates square art support across all relevant media types (movies, shows, seasons, episodes, audio, photos, collections, playlists)

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
plexapi/mixins.py	Adds three new mixin classes for square art functionality with lock/unlock, upload, set, and delete operations
plexapi/media.py	Defines the SquareArt resource class
plexapi/utils.py	Registers the squareArt tag type with ID 325
plexapi/video.py	Adds SquareArtMixin to Movie, Show, Season, Episode classes and SquareArtUrlMixin to Clip
plexapi/audio.py	Adds SquareArtMixin to Artist and Album classes, SquareArtUrlMixin to Track
plexapi/photo.py	Adds SquareArtMixin to Photoalbum and SquareArtUrlMixin to Photo
plexapi/collection.py	Adds SquareArtMixin to Collection class
plexapi/playlist.py	Adds SquareArtMixin to Playlist class
tests/test_mixins.py	Updates test helper to include square art delete operations and adds test functions for square art
tests/test_video.py	Adds square art test calls for Movie, Show, Season, and Episode
tests/test_audio.py	Adds square art test calls for Artist, Album, and Track
tests/test_photo.py	Adds square art test calls for Photoalbum
tests/test_collection.py	Adds square art test calls for Collection
tests/test_playlist.py	Adds square art test calls for Playlist

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