Have a staging website to build planned languages, with a resilient build

Originally created by @Anonymous on #15077 (Redmine)

This is part of the point “Integrate the platform with our Git and ikiwiki infrastructure”. We want to have a publicly accessible copy of our website running on the translation platform VM. This copy shall use Weblate’s Git repository and regularly build from it’s master branch our website.

This ticket is about

- installing the website on the machine

- make it accessible under some sort of subdomain (preprod.tails.boum.org) - or something similar
- set up a cron job do build planned languages

Feature Branch: feature/15077-add-staging-website

Parent Task: tails#15079 (closed)

Subtasks

• #12340 (closed)
• #12341 (closed)
• tails#12342 (closed)
• #15078 (closed)
• tails#15568 (closed)
• tails#15625 (closed)

Related issues

• Has duplicate tails#12311 (closed)
• Blocks tails#15084 (closed)