(lakehouse-prep-1) define_python_dagster_type API; metadata_fn -->…

Authored by schrockn on Jul 10 2019, 6:04 PM.


(lakehouse-prep-1) define_python_dagster_type API; metadata_fn --> typecheck_metadata_fn

As I'm working on the lakehouse prototype I'm going to be throwing up some
diffs of API changes/improvements resulting from those changes. For this I've
found that having a top-level API define_python_dagster_type is much more natural
than inheriting from PythonObjectType directly. As the term metadata_fn is too general
and confuses with other contexts where we use the term metadata.

This also reintroduces a changelog

Test Plan: Buildkite

Reviewers: alangenfeld, max, natekupp

Reviewed By: alangenfeld

Differential Revision: https://dagster.phacility.com/D576