Refs #25995 -- Documented that JSONField doesn't handle sophisticated serialization.

    its Python native format: dictionaries, lists, strings, numbers, booleans

    and ``None``.

    If you want to store other data types, you'll need to serialize them first.

    For example, you might cast a ``datetime`` to a string. You might also want

    to convert the string back to a ``datetime`` when you retrieve the data

    from the database. There are some third-party ``JSONField`` implementations

    which do this sort of thing automatically.

    If you give the field a :attr:`~django.db.models.Field.default`, ensure

    it's a callable such as ``dict`` (for an empty default) or a callable that

    returns a dict (such as a function). Incorrectly using ``default={}``