WIP - Schema validation support for Pydantic and Marshmellow

[tabotkevin]

check examples/schema_input_validation.py

"""Decorator for parsing and validating input schema.
Supports both Pydantic and Marshmallow.

Usage::
import time

from pydantic import BaseModel
import responder

class Item(BaseModel)
    name: str

api = responder.API()

@api.route("/create")
@api.trust(Item)
def create_item(req, resp, *, data):
    @api.background.task
    def process_item(item):
        time.sleep(2)
        print(item)   # e.g {"name": "Monster Hunter"}

    process_item(data)
    resp.media = {"msg": "created"}

"""