[FEAT] Upgrade to `Pydantic v2`

[jjfantini]

This will allow multiple benefits.

Use cases:

• multiple values allowed for aliases with AliasChoices and AliasGenerator

I need to validate a df that can have multiple names for a specific column. Let's say it could be col1 or `col[1-10]'.

I have a df that is created, and the column names can be a few different things but the same column, and I need a way to validate all the possible names. I've tried multiple things, custom validators, creating a model dynamically, and they have yet to work.

[jjfantini]

@JakobGM

[brendancooley]

Running list of todos here, perhaps we can farm these off into narrower issues if the implied solution is precise enough:

• [x] pydantic.error_wrappers.ErrorWrapper has been deprecated, need to update validation error reporting to conform to pydantic's new style
  • It looks like @thomasaarholt has some work on #4 to support the printing of data frame validation error messages
  • the library currently handles dataframe validation in patito.validation._find_errors, but pydantic expects validation to occur at the model level, which makes conforming to pydantic's error handling style somewhat difficult. Perhaps we could brainstorm a more "pydantic2" way of running validation on dataframes.
• [x] subclass/extend pydantic's Field (or FieldInfo) to handle patito custom attributes (unique, derived_from, dtype, constraints, others?)
• [x] workaround (or polars-side solution) to support the json serialization of polars DataType and Expr objects, to address serialization errors when calling BaseModel.model_json_schema() on models that contain polars elements.

---

some wip on validators here. The data frame validation logic doesn't quite map to the way pydantic v2 expects validation to occur, so I more or less ported over the pydantic v1 validation error reporting system into patito. It looks like this is where @thomasaarholt was headed with his PR. all tests in test_validators now passing except those that have serialization issues with json_schema_extra fields.

---

wip on extending FieldInfo here

---

fully operational prototype for the upgrade is up at #32