Add OpenStreetMap login to Datasette

I plan a project with geodata and some user interaction. Of course the plan is to use Datasette to build this idea. The first step to realize this is to build some kind of authentication and because of the geodata space using OpenStreetMap OAuth2 seems like the logic choice.

Writing a plugin to log into OSM was mostly copy/paste and some minor changes to the code from a project of Simon Willison: datasette-auth0.

The readme for the datasette-auth-osm plugin contains all the instructions to setup and a demo shows how it looks like. After successfully logged in the OpenStreetMap username is shown on the top right of the navbar.