feat: default value example working

[markdoerr]

Working example for the default-value pull request: socotecio/django-socio-grpc#255

( Issue: Fix/default value #255 )

[AMontagu]

Hello @markdoerr

We finally merge the defaults values (we blocked it for important internal release) as 0.22.0. You can now use this stable release on this MR and I can merge it

[markdoerr]

Merci @AMontagu,
this is good news ;) - I already used a pre-release version (0.21.5).
There is one issue, left, which I would like to discuss with you:
When one uses an abstract model, then the ForeignKeys of child classes are not "inheriting" the correct properties:

Example: In
https://gitlab.com/LARAsuite/lara-django-base/-/blob/master/lara_django_base/models.py?ref_type=heads
I defined the ExtraDataAbstr model with two optional fields, data_type and media_type (which are both optional == blank=True and null=True).
When I subclass ExtraDataAbstr, the ForeignKey fields are generated as non-optional in the .proto file. This is not the case with optional ForeignKeys of non-abstract models.

Do you have an idea, why ? I guess it has something to do with the depth of recursion to explore the model structure in the .proto generator, or that it currently does not fully support abstract models.