Toaster: transitioning to Django-2.2 soon [YOCTO #13207]

Hi all,

I wanted to let people know that I will be transitioning Toaster to Django-2.2 for master and YP-3.1. Recent changes to SQLite-3.26 and Python-3.7 now used in the current hosts have made the Django-1.x line unsupportable (by the Django community's choice).

I have posted a relatively large patch set here for everyone's review, which I will soon commit to bitbake:
   http://git.yoctoproject.org/cgit/cgit.cgi/poky-contrib/commit/?h=dreyna/toaster/django_2_2_13207&id=117fc2dd7dc220c516309477f2cbe2134f1bd5db

My main concern is that there was some core API changes which required updating the existing migration files (which one normally never touches). That change was to add "on_delete=models.CASCADE" for foreign tables. This simple change should not affect existing databases and their migration, but I am doing extra testing to make sure I understand the impact.

- David