OSMCha tech priorities

[willemarcel]

• Upgrade overpass server hardware on Hetzner
• Try to discover why the osm-adiff-service gets stuck
• Add User-Agent header to all request directed to osm.org servers (osmcha, osmcha-django, osmcha-frontend and osm-adiff-service repository codes needs to be reviewed)
• Upgrade Django version (There is a WIP PR at Update/django 3215 OSMCha/osmcha-django#634)