Propagate 'default' from model_field to serializer field

[john-parton]

Description

This is an attempt to fix #7469

It's actually really simple. ModelSerializer.build_standard_field looks for the default key in the dictionary returned by get_field_kwargs, but get_field_kwargs never returns a dictionary with that key.

Edit

I was personally motivated to fix this because I wanted the default value to appear when you do an OPTIONS query. That's incredibly tedious without this fix. More info here: #8003

[SchrodingersGat]

@john-parton I have been trawling through the DRF documentation trying to work out how to use the default parameter for a django model by "default" for the fields in a ModelSerializer.

It appears that this is not actually possible (until this PR is merged)?

I would have assumed that this was a natural and reasonable feature to expect! +1 to getting this feature merged it this is not already the case.

[benesch]

Thanks, @john-parton, I just really wanted this too! There were are a few test failures here that I'm going to clean up and resubmit as a new PR.

[benesch]

Submitted as #8130.

[john-parton]

Superseded by #8130