Django-rest-form-fields

Features
1. Added ability to add underscore symbols in `UrlField`

Features
1. `IdField` max value can be now limited globally with `ID_FIELD_MAX_VALUE` django settings (in settings.py)

Dependencies
1. Made `pytz` and `jsonschema` optional dependencies

CI
1. Replaced python 3.6 with python 3.11, 3.12

Bug fixes
1. Fix ModelForm issue in django 3.0+, which caused fields with required=False validation by model fields

Testing
1. Replaced django 2.1 with django 4.0 in test matrix