Deprecation warnings from marshmallow

[lindycoder]

Hello!

First, thank you for the tool!

I noticed there are some warnings from marshmallow that needs to be addressed:

since marshmallow>=3.10.0 marshmallow-code/marshmallow@013abfd

RemovedInMarshmallow4Warning: Passing field metadata as a keyword arg is deprecated. Use the explicit `metadata=...` argument instead.

since marshmallow>=3.13.0 marshmallow-code/marshmallow@1db1a8a

RemovedInMarshmallow4Warning: The 'default' attribute of fields is deprecated. Use 'dump_default' instead.

Currently this project supports marshmallow>=3, so here are some ideas:

• Fix both warnings and bump requirements.txt to marshmallow>=3.13.0
• Keep current requirements and try to use new features in code, like use metadata= and dump_default= when detecting marhsmallow<3.13 (not sure if possible)
• Ignore those and change the requirements to marshmallow>=3,<4

Another idea?

I'll be happy to help following your guidance.

Thank you