Feat: districts Django app setup

[lalver1]

Closes #63
Part of #65

This PR sets up the districts Django app and adds an initial District model (with associated fixtures).

Notes

We assume these patterns

• A models.py module per Django app.
• A migrations folder per Django app (python manage.py makemigrations will run through each app and make the migrations). This means that in makemigrations.sh we will have several lines like python -m black pems/district/migrations/*.py, one per app.
• A local_fixtures.json file in the root Django project .

[github-actions]

Coverage report

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
pems/districts
admin.py
apps.py
models.py
urls.py					5-6
pems/districts/migrations
0001_initial.py
Project Total

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[thekaveman]

This is a nitpick, I think the name of the app districts (plural) reads a little better than the singular district.

E.g. thinking about the URL structure, we'll want something like /districts/<id> -- not that this ties exactly to the app name, but the consistency seems good.

Thoughts?

[lalver1]

No, this is a good suggestion. I'm actually seeing this pattern in the Miro board, but I don't know why I overlooked it (devices, instead of device, etc.). And yep, the URL structure can be completely different from the app name but I agree that they need to stay consistent. I'll make this change and update it 👍

[thekaveman]

Looks good 👍

Nice to have a fixtures file with all the Districts defined to get started with.