Support for Decimal type

I’ve been using my own implementation of a Decimal type – maybe it should be included as a standard type?

from graphene.types import Scalar
from graphql.language import ast

class Decimal(Scalar):
    """
    The `Decimal` scalar type represents a python Decimal.
    """
    @staticmethod
    def serialize(dec):
        assert isinstance(dec, decimal.Decimal), (
            'Received not compatible Decimal "{}"'.format(repr(dec))
        )
        return str(dec)
    
    @staticmethod
    def parse_value(value):
        return decimal.Decimal(value)
    
    @classmethod
    def parse_literal(cls, node):
        if isinstance(node, ast.StringValue):
            return cls.parse_value(node.value)

[picturedots]

Ok, I will take a crack at it when I have a chance. I’ll have a look at the existing tests for other types for some examples.

[jkimbo]

(also it is there in the API documentation at least! https://docs.graphene-python.org/en/latest/api/#graphene-scalars)