Implement mesh tile server

[davidwyld]

Since meshes are large, it's not practical to serve them up via a simple http request similarly to routes.

The best solution I've found is probably to use an out of the box tile server, specifically maplibre/martin

Note: This is already under some exploratory development on the dw/serve_mesh_vector_tiles branch.

To do

• Use postgis extension/container in docker compose stack,
• Use martin container in docker compose stack,
• On mesh save/create, create mesh polygon db entries, with cellbox metadata,
• Consider managing cleanup of mesh polygons in db
• Work out how to document in api schema,
• In deployment config, enable postgis extension,
• In deployment config, include running db script to add mesh vector tile (mvt) function
• In deployment config, install additional dependencies for geodjango, e.g. PROJ, GDAL
• In deployment config, set up martin as a service under systemd
• In deployment config set up reverse proxy under apache/httpd
• Document deployment
• Integrate into frontend
• Testing of django elements