feat(conversation): Add option to allow deleting one-to-one conversat…

[nickvergessen]

…ions

🛠️ API Checklist

🚧 Tasks

• 1:1 conversation can be deleted permanently for both participants
• Any of the 1:1 conversation participants can delete the conversation
• The option “permanently delete the whole conversation” means that all messages will be deleted for both participants
• The option “permanently delete conversation” must be implemented instead of “leave conversation” for 1:1 chat
• For group chats leaving conversation and deletion policy remains unchanged, like it is now.

🏁 Checklist

• Confirm with Android: Check canLeaveConversation and canDeleteConversation handling talk-android#4570
• Confirm with iOS: Check canLeaveConversation and canDeleteConversation handling talk-ios#1932
• ⛑️ Tests (unit and/or integration) are included or not possible
• 📘 API documentation in docs/ has been updated or is not required
• 🔖 Capability is added or not needed

[ShGKme]

Tested