🔖 Thalia Website v1.16.1

Errors resolved

• Fix registration problems (!864 (merged))
• Fix typo in push notification devices viewset (!862 (merged)) push notifications
• Fix member expiration emails (!856 (merged)) members
• Fix conditions for showing presence and payment on the event page (!845 (merged)) events
• Fix 'to' email address in email change confirmation email (!842 (merged)) members

New functionality

• Add privacy policy checkbox to renewal form (!855 (merged)) registrations
• Add optins to members registration form (!849 (merged)) registrations

Technical changes

• Get CELERY_BROKER_URL from env vars as a whole (!852 (merged))
• Make phone number optional during member registration (!848 (merged)) registrations