build.sh replaces docker-compose as an image build tool. Instead, all
OpenSlides services can be built using this script which offers various
important options such as tagging and configurable defaults.
The now-redundant build instructions have been removed from the YAML
templates.
The almost identical server and client build scripts have been made
fully identical.
We have decided against including an insecure default key with a mere
warning. Therefore, unlike the admin and user secrets, the availability
of this secret is a hard requirement. The instance will not be able to
start before a secret has been generated manually or by a management
tool.
