Thanks to @dani-garcia for the review!

No need to use two different base images. Debian buster is pulled later
anyway so we can just use it for the vault stage as well.

My reason for this change is partly to avoid redundancy and partly to
make it easier to build everything yourself. When all the build
environment is based on Debian than you just have to figure out how to
build a Debian Docker base image (ref:
https://github.com/ypid/docker-makefile).

Add Github build Action

Collapsed log messages from 3 lines per request to 2 and hidden the ones valued as less informative.
Use LOG_LEVEL debug or trace to recover them.

Removed LOG_MOUNTS and bundled it with LOG_LEVEL debug and trace.

Removed duplicate error messages

Made websocket not proxied message more prominent, but only print it once.

Create an issue template

I'm not sure if this is needed but I think it could be useful in lessening the workload.

Implement change-email, email-verification, account-recovery, and welcome notifications

Added netcup domains to global domains

Add an option to fetch and parse href="data:image"