Assign cards to TODO: comments

[DavidBiddle]

What problem does this pull request solve?

Trello card: https://trello.com/c/hK0527GN/219-review-todo-comments-and-make-product-cards-for-any-that-are-still-relevant

As part of firebreak work we've reviewed the outstanding TODO: comments in this repo and made tech debt cards for them.

This PR adds references to those tech debt cards in the codebase, so that anyone tackling the TODO tasks in future can easily check the card for additional context.

Things to consider when reviewing

• Ensure that you consider the wider context.
• Does it work when run on your machine?
• Is it clear what the code is doing?
• Do the commit messages explain why the changes were made?
• Are there all the unit tests needed?
• Do the end to end tests need updating before these changes will pass?
• Has all relevant documentation been updated?

[github-actions]

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