Is your feature request related to a problem? Please describe.

The package marshmallow-enum, which Indico depends upon, has been unmaintained since 2022-10-20 (see the source repository).

I think it would be a good idea to get rid of it.

Describe the solution you'd like

The reason why the package was archived is that marshallow has supported Python's enum classes since version 3.18.0 (see the documentation and the marshmallow-enum issue).

I'd like to replace marshmallow_enum.EnumField with marshmallow.fields.Enum and remove the marshmallow-enum dependency.

From a quick look at the code, a simple search/replace approach would work. I can open a PR if you wish.

Describe alternatives you've considered

Another option would be to include the package code directly in Indico, as it's very simple, but it would be a waste not to use the out-of-the-box support in marshmallow.

Additional context

N/A