fix: constrained unions

guacs commented 8 months ago

Fix the parsing of the constraints from union types for Pydantic v2 models
- Before there used to be special handling of optional types, but that's not needed since optional types are also unions and so optional types should also be handled the same way as union types where we just ignore NoneType. This makes the change the same as that of FieldMeta.from_type (as changed in #491).
Fix the way the annotated types are handled when calling FieldMeta.from-type by using the actual type that is annotated rather than Annotated[type, ...]
- Due to the change in FieldMeta.type_args in #491, Annotated[List[str], MinLen(10)] now returns List[str] whereas before it would have returned str as the child. This results in the children for the FieldMeta corresponding to the annotation Annotated[List[str], MinLen(10)] to be List[str] instead of str. Unwrapping the annotation to get the actual underlying type fixes this problem since now FieldMeta.type_args will return str in this case instead of List[str].