🚀 [Feature] Invite only

Created by: ulfgebhardt

🚀 Feature

Invite only

Allow only people with a valid invite code to register

• 1 user per invite code
• How will the UI look?
• What is already implemented?
• Can we make that an option to turn this feature on/off?

Please make followup issues for everything that comes up - we will decide which ones we will do during the prepare phase