karrot docker production setup

A setup for karrot using docker intended for production use to support easy self-hosting.

TODO

• email?
• make maxmind account optional
• document usage
• handle secrets properly
• make ports configurable?
• db password?
• security practises?
• prebuild/push docker images somewhere...
• push notification config?
• CSP headers
• app download URL?
• redis storage volume?
• worker healthcheck?
• add stuff for co-op cloud setup...