Run import on separate machine

[jbruechert]

The import of openstreetmap data needs a large amount of RAM and CPU time. We should run it on a separate server in order to not impair the performance.

Maybe Spline has enough resources to host a separate import vm, but I'm not sure. The import vm needs ~128G RAM, and ideally ~200GB SSD storage.

I would like to run the import publicly visible, for example on GitHub Actions, in order to enable more people to fix things without having access to the server.