Rework auth with more information and a constant client id

[wheresfrank]

PlexAuthController Refactor and Improvements

This pull request introduces significant improvements to the PlexAuthController, enhancing its reliability, error handling, and overall functionality for Plex authentication.

Key Changes

1. Consistent API Calls: Introduced a unified plex_request method for all Plex API interactions, ensuring consistent headers and error handling across all requests.
2. JSON Parsing: Updated all methods to use JSON parsing instead of XML, aligning with Plex API's preferred response format.
3. Rate Limiting Handling: Implemented an exponential backoff strategy in the generate_plex_pin method to handle Plex API rate limiting (HTTP 429 errors).
4. Improved Error Handling: Added comprehensive error handling and logging throughout the controller, including specific handling for JSON parsing errors.
5. Consistent Client Identifier: Introduced a VOTERR_CLIENT_ID constant, ensuring a consistent client identifier is used across all Plex interactions.
6. Enhanced Plex Auth URL Generation: Updated the plex_auth_url method to include all necessary parameters and headers required by the Plex OAuth flow.
7. Robust Callback Handling: Refactored the callback method to handle potential nil returns from user data and server ID fetching operations.
8. Logging Improvements: Added detailed logging throughout the authentication process for better debugging and monitoring.

Impact

These changes address several issues:

• Eliminates the "Security Alert" warning during Plex authentication by using a consistent client identifier.
• Reduces the likelihood of rate limiting issues with Plex API.
• Improves the reliability of the authentication process by handling various edge cases and potential errors.
• Enhances debugging capabilities with more comprehensive logging.

Testing

The updated controller has been tested locally with the following scenarios:

• Successful Plex authentication flow
• Handling of rate limiting errors
• Error cases such as failed pin generation and user data fetching