chore: add basic pre/post check for broker fee migration

[kylezs]

Pull Request

Checklist

Please conduct a thorough self-review before opening the PR.

• [x] I am confident that the code works.
• [x] I have written sufficient tests.
• [x] I have written and tested required migrations.
• [x] I have updated documentation where appropriate.

Summary

Just basic checks to ensure the translate is decoding correctly, the rest is type safe.