Add support for Pydantic V2

[exg]

See https://docs.pydantic.dev/latest/migration/

[aviramha]

Thanks for your contribution!
Before merging this, we need to add tests, similar to what we have in https://github.com/aviramha/ormsgpack/blob/master/tests/test_pydantic.py

[exg]

Thanks for your contribution! Before merging this, we need to add tests, similar to what we have in https://github.com/aviramha/ormsgpack/blob/master/tests/test_pydantic.py

What tests do you have in mind? The existing tests cover V2, and pass with my change. Note that the tests use pydantic 2, as the pydantic dependency is not pinned in tests/requirements.txt.

[aviramha]

Ah, my mistake - all is good then, just need DCO.