Upgrade to Pydantic v2

[ammar92]

Changes

This updates the Pydantic package to the latest major version. Please keep in mind that this should be tested properly:

• It should work on "old" data
• The OOI creation forms should still work
• Onboarding flow works as usual
• OOI detail and listing views work as usual

Issue link

Closes #1841

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Code Checklist

• All the commits in this PR are properly PGP-signed and verified;
• This PR only contains functionality relevant to the issue; tickets have been created for newly discovered issues.
• I have written unit tests for the changes or fixes I made.
• For any non-trivial functionality, I have added integration and/or end-to-end tests.
• I have performed a self-review of my code and refactored it to the best of my abilities.

Communication

• I have informed others of any required .env changes files if required and changed the .env-dist accordingly.
• I have made corresponding changes to the documentation, if necessary.

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Checklist for code reviewers:

Copy-paste the checklist from the docs/source/templates folder into your comment.

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Checklist for QA:

Copy-paste the checklist from the docs/source/templates folder into your comment.