Upgrade to pydantic v2 #520

[joshdimanteto]

This PR will close #520

Description

• Update pydantic to version 2
• Change field_validator that are use repetitively to use annotated pattern

Testing Instructions

Add a set up instructions describing how the reviewer should test the code

• Review code
• Check GitHub Actions build
• If icatdb Generator Script Consistency Test CI job fails, is this because of a deliberate change made to the script to change generated data (which isn't actually a problem) or is here an underlying issue with the changes made?
• Review changes to test coverage
• Does this change mean a new patch, minor or major version should be made? If so, does one of the commit messages feature fix:, feat: or BREAKING CHANGE: so a release is automatically made via GitHub Actions upon merge?
• {more steps here}

Agile Board Tracking

Connect to #520

[patrick-austin]

Had a few thoughts on whether some of the pydantic functions are actually required or whether they can be simplified, but I've not actually run the code so some of my suggestions might be wrong (it's based on vague memory of how validation etc. works).

Will try and do some experimentation to check these suggestions make sense at some point, but it might be quicker for you to have a go if you have time?

[patrick-austin]

Glad those suggestions did actually work / make sense in the end. I haven't done any targeted manual testing (just checked that the API starts and I can submit an arbitrary query OK), since this didn't add/change any specific functionality and the tests are passing on the CI. I'm happy to approve based on that but let me know if you think there's something worth manually checking in more detail.