* Use requirements.txt for automated version bumps.
Move the Mailman requirements into requirements.txt file so that
we can use dependabot for automated version bumping.
* Remove constraint on mistune
* Add requirements file to dockerfile
* Add dependency on tzdata
* Test dependabot for Dockerfiles.
* Also for github actions
* Update dependabot.yml
* Fix urls.py for new versions of Django
* Fix urls.py for postorius.
* Bump dependency on Postgresql.
* Bump dependency on Django
* Add dependency on tzdata.