fix: implement create_user_task workaround

[asajjad2]

What are the relevant tickets?

#6807

Description (What does it do?)

This PR implements a workaround for an issue in the django-user-tasks library where the create_user_task signal handler fails with TypeError('tuple indices must be integers or slices, not str') when processing Celery tasks with protocol version 2 (the default in recent Celery versions). This occurs when processing our task_upload_course_s3 task.

The django-user-tasks library was designed for Celery's protocol version 1, but our application uses protocol version 2. This causes errors in logs when tasks are published, though the tasks themselves still execute.

Changes:

• Disconnect the original signal handler
• Connect a wrapper function that detects the protocol version
• For protocol v2 messages, convert them to protocol v1 format before passing to the original handler
• For protocol v1 messages, pass them through unchanged

[pdpinch]

Since this is a bugfix, I think we should open an upstream PR in edx-platform instead of creating a new plugin.