Refactor pydantic fundamentals and mixins

[devraj]

utils.py in schema has a number of Mixins, these help with some base assumptions like Identity, Date Time of creation and update of models.

Identity inherits from pydantic BaseModel and creates a method resolution issue.

This pattern should be rethought to also provide a generic implementation of #27

Perhaps a BaseModel provided by the package that has the base configuration requires and Mixin simply add garnish and not provide a BaseModel resolution