Add support for self-hosted reverse geocoding (Photon)

[zvea]

Currently, reverse geocoding requires streaming location data to a third-party provider. For privacy reasons, it would be nice if the app was able to use a self-hosted instance of Photon.

• Photon repo: https://github.com/komoot/photon
• Public API and demo: https://photon.komoot.io/

This would also make for a nice integration with DaWarIch (https://dawarich.app/) since it already supports self-hosted Photon (info).

• App build number: 2.5.3
• Installation source: Google Play

[jpmens]

I wonder how many people would go to the trouble of installing/self-hosting Photon:

• 200GB storage for indexing
• Java
• PostgreSQL
• Elastic (unless I misread)
• .. ?

[zvea]

I don't have any insight into the install base of Photon (except that I, for example, host my own instance).

What I do know is that spinning it up involves a single Docker command: https://github.com/rtuszik/photon-docker