Integration with patata

[lvps]

0. Synchronize patata database with OwnCloud (it's manual, just make a systemd unit (also: not really relevant to this issue))
1. Read the sqlite database from OwnCloud
2. When someone is logging out, check if there is any completed task between login time and now
3. If there is any, check if the maintainer is the person logging out (compare username)
4. If it is, add it to the list of completed tasks, named completed_tasks
5. Add to the logout message ', '.join(completed_tasks)

[lvps]

Can be done through Deck APIs now