closeConversation
Permanently closes the conversation.
After closing, no further messages can be sent or received on this conversation. This action is irreversible. To start a new conversation after closing, create a new ConversationClient with a fresh UUID via CoreClient.conversationClient.
To end a session while keeping the conversation open for future use, use endSession instead.
Return
Result.Success if the conversation was closed, or Result.Error if the operation failed.