Add option to deactivate handling of chat message state by participant in group chat.

src/chat/chat-message/chat-message.cpp

@@ -66,7 +66,11 @@ void ChatMessagePrivate::setIsReadOnly (bool readOnly) {
 void ChatMessagePrivate::setParticipantState (const IdentityAddress &participantAddress, ChatMessage::State newState) {
 	L_Q();
 
-	if (!(q->getChatRoom()->getCapabilities() & AbstractChatRoom::Capabilities::Conference)) {
+	if (!(q->getChatRoom()->getCapabilities() & AbstractChatRoom::Capabilities::Conference)
+		|| (linphone_config_get_bool(linphone_core_get_config(q->getChatRoom()->getCore()->getCCore()),
+			"misc", "enable_simple_group_chat_message_state", TRUE
+		))
+	) {
 		setState(newState);
 		return;
 	}

tester/group_chat_tester.c

@@ -2635,6 +2635,9 @@ static void imdn_for_group_chat_room (void) {
 	linphone_im_notif_policy_enable_all(linphone_core_get_im_notif_policy(marie->lc));
 	linphone_im_notif_policy_enable_all(linphone_core_get_im_notif_policy(pauline->lc));
 	linphone_im_notif_policy_enable_all(linphone_core_get_im_notif_policy(chloe->lc));
+	linphone_config_set_bool(linphone_core_get_config(marie->lc), "misc", "enable_simple_group_chat_message_state", FALSE);
+	linphone_config_set_bool(linphone_core_get_config(pauline->lc), "misc", "enable_simple_group_chat_message_state", FALSE);
+	linphone_config_set_bool(linphone_core_get_config(chloe->lc), "misc", "enable_simple_group_chat_message_state", FALSE);
 
 	// Marie creates a new group chat room
 	const char *initialSubject = "Colleagues";