Handle related_model specially in FieldSignature.
Review Request #10295 — Created Nov. 1, 2018 and submitted
related_modelas a special
argument, and a later version of that change got rid of that in favor of
a field attribute. The original idea was correct, as the equivalent
field attribute for
Fieldclasses required a model, whereas this
version represented a class path string.
This change restores this as its own attribute, and makes it easier to
FieldSignaturewith a related model and field attributes
all at once. Diffing has been updated to factor this in as well.
Tested along with other pending changes. Related model handling worked.