Create partdb-release-script.sh

[d-buchmann]

I finally tested the update script and it worked =) (reference: #720)

Prerequisites:

• Direct installation on Debian 11 or similar
• MySQL or MariaDB configured
• Webserver apache2
• The constants have to be adjusted to your environment.
• The script expects database_user and database_password as arguments.

The (guided) update process goes through ~4 stages: 0: check for new release 1: put current site into maintenance mode (requires an extra vhost to be set up...meh) 2: backup partdb database (only mysql at the moment...meh); git pull 3: Build according to the docs, transfer required files to testing location (yet another vhost...) 4: Transfer testing site to live enviroment, end maintenance mode

The process can be interrupted at any stage, by errors or by user interaction. Resumption is possible through a stagefile.