Consider Adding Testing Objects

[ghickman]

The tests in job-server require some extra set up now that the Pipeline model enforces various pieces of the config. Could we extract some of those ideas into this library as helpers for testing?

Copying how factory_boy builds ORM models some kind of pytest fixture which ensures all the correct values are set for the given input.

Something like:

def pipeline(data: dict[str, Any]) -> Pipeline:
    if "version" not in data:
        data["version"] = "3"

    if "expectations" not in data:
        data["expections"] = {"population_size": 100}

    return Pipeline(**data)