Is your feature request related to a problem? Please describe.
Currently, the units model is not hashable although the content should be immutable and, hence, frozen.
But due to the missing Config in the model the __hash__ function is not generated by pydantic.

Describe the solution you'd like
I would like to add the following content to the model:

class Unit(BaseModel):
    ...

    class Config:
        extra = 'ignore'
        allow_population_by_field_name = True
        allow_mutation = False
        frozen = True
           

Describe alternatives you've considered
Inherit, the Unit model and add a specific Config object. However, this may lead to inconssitency

Additional context
Use case:
I have a list ob sensors that also contains information about the unit.
For mapping measurements to the sepcific sensors I regularly must loop throuth this list. Therefore, caching such lookup can be wuite useful. Caching though requires hashing of the Objects in the list that I qant to operate on.