Add a deployment tool

[Fohlen]

With the merge of #27 the SETUP.md will get more complicated. It would be good to have a simple tool to manage this.

Basically what it should do is the following:

• provide a convenient setup experience. ./make (or comparable) should be sufficient to get up and running
• provide means to configure the setup (especially for authentication)
• provide means to manipulate the fixtures, this blocks Add way to bootstrap fixtures #12
• provide a way to easily use the migrate and psql command lines. e.g: provide a forwarding interface to migrate, and a psql command to connect to the database

If possible, use an existing tool to accomplish this (less code is better code, yay ✨)

[Fohlen]

After some time of thought here is the plan of action:

• host a Dokku instance ourselves on a Hetzner CX11 with Backups (~3 euro / month)
• migrate away from the old (Docker-based) instance to the Dokku instance
• close this issue