Starts the securejoin protocol with the QR
This will try to start the securejoin protocol for the given QR
invite. If it
succeeded the protocol state will be tracked in
This function takes care of handling multiple concurrent joins and handling errors while starting the protocol.
ChatId of the created chat is returned, for a SetupContact QR this is the 1:1
chat with Alice, for a SecureJoin QR this is the group chat.