protocol InviteDelegate : NSObjectProtocol
The protocol to receive the result of the invite action.
Reports the status of the invite action. |invitationsIds| holds the IDs of the invitations sent by the user. |error| is nil upon success. Otherwise, it will contain one of the errors defined in FIRInvitesError.h.
optional func inviteFinished(withInvitations invitationIds: [String], error: Error?)