Replace SettingsModel by SettingsGateway

Addresses #9 (closed)

What does this MR do?

Replace SettingsModel by SettingsGateway

How confident are you it won't break things if deployed?

Confident

What to test

Beta testers should focus on all preference related settings.

Test as a Foodsharer/Foodsaver

• Own preferences

  • Subscriptions/Benachrichtigungen: un-/subscribe to newsletter and/or chat, food share point updates
  • sleep status
  • changing the email-address
  • ...

• Follow a food share point, forum threads ...

Test as a orga member

• Change the settings of a store
• Change the settings of a food share point
• Change the settings of a foodsaver

Downgrade a Foodsaver

1. Login as Orga
2. Edit a foodsaver -> Set the role to Foodsharer
3. Login as the downgraded foodsharer
4. Assert that the foodsharer is not able to start a quiz
5. Assert that the foodsharer is not a member of any team, workgroup, ...

Upgrade a Foodsaver

1. Login as Orga
2. Edit a foodsaver -> Set the role to something higher
3. Login as the upgraded foodsharer
4. Start a quiz
5. Assert that the foodsharer has to do the next higher quiz

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes -> Introduced a new DBConstant InfoType
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))
• Once your MR has been merged, you are responsible to update the #foodsharing-beta Slack channel about what has been changed here. They will test your work in different browsers, roles or other settings