Fix examples to work with Pydantic V2, add test for example

Support pydantic 2

chore: drop testing for EOL Python 3.7

fix: optional union type errors

build: bump version to 0.5.0

This version marks support of Pydantic V2 and python 3.12, and drops support for Pydantic V1

fix: allow support for str|None or Union[str|None] in input type

fix: default value pydantic undefined

fix: default value not working for input types

Update poetry.lock

feat: added support for v2

deprecated: pydantic v1