Allow models to be specified more pythonically - with type hints, perhaps use pydantic for type checking

[gresnick]

Currently it doesn't seem possible/useful to assign type hints to fields, for example

class User(mdl.Model):
    name: str = mdl.TextField()

Ideally, using a validation library such as pydantic

class User(mdl.Model):
   name: str

Reasons for the suggestion:

• more pythonic (concise, using built-in type hints)
• potentially support more types out of the box
• allow pydantic models instead of NestedModel -> cannot accidentally .save() !
• robust validation provided by third party validation library