[FEAT] Load council geometries and serve geojson from API

[mattyweb]

Description

Want to load the current GeoJSON into the database and create and endpoint that will serve it up from the API.

The immediate benefit is that the client won't need to bundle the (huge) file and we'll be able to update the GeoJSON without needing new client releases.

The longer term benefits are that we'll be able to do spatial queries in the app (e.g. calculate centroids, query for points by distance, etc.). We will also be able to automate the process of downloading the new GeoJSON when there are changes.

Action Items

1. Need to use postgis docker image
2. Need to enable postgis extension with alembic
3. Need to load a table with geometry (MULTIPOLYGON) from current GeoJSON
4. Need to add model and ORM query
5. Need to add endpoint

Resources

https://geoalchemy-2.readthedocs.io/en/latest/orm_tutorial.html
https://geohub.lacity.org/datasets/neighborhood-councils-certified/
https://postgis.net/docs/reference.html#Geometry_Accessors
https://github.com/jgriffith23/postgis-tutorial