sendDefaultMessageToChats

fun TalkApiClient.sendDefaultMessageToChats(receiverChatIds: List<Long>, template: DefaultTemplate, callback: (messageSendResult: PartnerMessageSendResult?, error: Throwable?) -> Unit)
fun RxTalkApiClient.sendDefaultMessageToChats(receiverChatIds: List<Long>, template: DefaultTemplate): Single<PartnerMessageSendResult>

기본 템플릿을 사용하여, 특정 채팅방에 카카오톡 메시지 전송.