Announcement done: https://de.wikipedia.org/w/index.php?title=Wikipedia%3AKurier&type=revision&diff=169848880&oldid=169847852
Deploying will be done similarly to Swedish:
* Anonymous users will get compact language links.
* Newly registered users will get compact language links.
* Already registered users will get compact language links if they had the beta feature enabled or if they didn't edit in 2017. Already registered users who edited in 2017 and didn't enable the beta feature will get the usual old language links.
* All registered users will be able to enable or disable this feature in the preferences.
Schedule: SWAT on 16 October 2017.
[ ] Deploy https://gerrit.wikimedia.org/r/#/c/364428/ to simplify the configuration. (Scheduled for SWAT on October 11.) (Amir)
[v] Create a patch to make it enabled on dewiki. (Simple, but depends on the previous point.) (Kartik)
[ ] Create a patch to migrate preferences, with correct dates for dewiki. (Amir)
[ ] Schedule SWAT. (Kartik)
[ ] Run the script to migrate preferences. (Kartik)
[ ] Deploy on October 2017. (Kartik)