Matt Bretl

- [ ] Nested composite types - [ ] Nullability (#124)

PostGraphile currently only respects the `@deprecated` smart comment on table columns, not constraints. Ref: https://github.com/graphile-contrib/pg-many-to-many/issues/11#issuecomment-518254772

By default, we should only expose functions/operators that are guaranteed to be compatible given a column's type details, namely: - base type: geography, geometry - subtype: Point, LineString, Polygon, MultiPoint,...