The current installation guide is not helping newcomers to install the app the exact same way as we did, because it is

• not clear to users that there is a reproducible docker installation (because it's placed way too far to the bottom in the guide)
• not working with the provided defaults:
  • atrain has dependency issues, during build stage and fails the entire compose build stage
  • the default mysql host is 127.0.0.1 but it should by mysql or connections will be rejected
  • it's not clear that npm does not need to be installed but can be used within sail
  • seeding is not explained

We therefore need to do the following:

• split the installation into INSTALL_DOCKER.md and INSTALL_MANUAL.md
• In INSTALLATION.md make it explicit to decide which of these installations to use, explain them and link them
• Link a tutorial on how to install docker (that is optimally platform-independent)
• add information to copy the .env from .env.example
• fix the default entries in .env.example
• fix the aTrain dependencies
• add a post-installation setup
• if possible, wrap all into one posix-conform shell script