Pydantic classes for all api's or OpenAPI definition

**Is your feature request related to a problem? Please describe.**
I'd like to use the Alpaca API in python and process the results as JSON. One way I can do this is to have pydantic classes for each of the API's or an OpenAPI v3 definition from which i can automatically generate the pydantic classes.

**Describe the solution you'd like**
I'm interested in any solution that allows me to validate the return of data from the API and allows the generation of JSON. Either pydantic classes for each API or an OpenAPI defintion from which I can generate my own definitions.

**Describe alternatives you've considered**
Writing my own set of Pydantic classes or hoping that there are no data errors from the api's.

**Additional context**
Add any other context or screenshots about the feature request here.