Add parameters validation against schemas

[kazz-s]

Is your feature request related to a problem? Please describe.
Every broker needs to implement validation.

Describe the solution you'd like
Implement a general solution in openbrokerapi.api module.

[eruvanos]

I took some more time for looking into this direction.
From the spec I do not see any hint about service brokers should implement the validation:

Platforms MUST support at least JSON Schema draft v4

This goes more into the direction of platform has to support this.
Still, I like the general idea to add some meaning to the schemas.

Right now I am not 100% sure about the current #123 (will follow up on this).

[eruvanos]

I also thing about doing some heavier lifting.

-> Switch to FastAPI (use Python type hints and Pydantic schema validation)

[vaxvms]

IMHO, validating parameters against schema in the broker make sense as we can free the broker writer from validating input data and get clearer error messages for users when parameters are wrong or missing.

[holec]

I like your package, it helped me quite a bit. I’m using it in a FastAPI application so having all of it in FastAPI would be nice. There is/was also fastbroker which sadly seems discontinued, maybe it can help as inspiration.

Having input parameters validation against a schema would be a very helpful feature.

[eruvanos]

I see the point of supporting easier schema validation. I am still not sure if it would be the right way to have it as a build in feature instead an opt in mechanism which can be easily setup via Pydantic.

I will consider this for the roadmap 2022.

Just to mention, I started to migrate this project to FastAPI Branch but did not make it, due to limited free time I could spend on this project.