Pydantic V2 support

[thomashlvt]

We are currently blocked on upgrading our app to pydantic==2.6.0 because interval-sdk requires pydantic<2.0.0. I'm not sure whether you actually depend on any V1 features, but supporting both would be some very welcome flexibility :)

Pydantic has a great migration guide

[jacobmischka]

I don't know of any particular v1 features we rely on, it's mostly been a matter of making time to do it :/

PRs more than welcome! 🙂