🔱 Refactor Celery implementation

[michaeljcollinsuk]

Context

Refactor the way that tasks are triggered and handled to be closer to those documented by Celery.

Currently there is a lot of custom code for sending and retrieving tasks, which I think is unnecessary and results in unnecessary duplication. It also makes it harder for developers to use the celery documentation and potentially makes it difficult for us to keep up to date with changes in Celery.

Refactoring will allow us to update celery quicker, which in turn will help us react faster to issues such as failed tasks triggering a high number of sentry alerts.. Example https://mojdt.slack.com/archives/C04M8224WCV/p1732871862102339

Proposal

Refactor implementation to be in line with Celery standards/best practices.

Spike requirements

No response

Definition of Done

• Identify areas of code to be refactored
• Ensure regression tests are in place
• Update the code
• Test implementation in the browser to ensure it works as intended

[github-actions]

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