Add support for Django 5.2

[peterfarrell]

• Update tox.ini Add django 5.2 to tox.ini
• Updated classifiers in setup.py
• Update GH actions matrix, add exclude section for unsupported versions of Python by Django version (e.g. Django 5.2 does not support Python 3.9)

[peterfarrell]

@peppelinux ready for review, all tests pass. Suggest to be released as 1.11.2 since there are not significant code changes other than test / tox matrixes.