[IMPROVE] Slack bridge: add support to threads (#15992)

Co-authored-by: Rodrigo Nascimento <rodrigoknascimento@gmail.com>
Co-authored-by: pierre-lehnen-rc <55164754+pierre-lehnen-rc@users.noreply.github.com>

app/slackbridge/server/RocketAdapter.js

@@ -469,6 +469,13 @@ export default class RocketAdapter {
 			if (slackMessage.edited) {
 				rocketMsgObj.editedAt = new Date(parseInt(slackMessage.edited.ts.split('.')[0]) * 1000);
 			}
+			rocketMsgObj.slackTs = slackMessage.ts;
+			if (slackMessage.thread_ts) {
+				const tmessage = Messages.findOneBySlackTs(slackMessage.thread_ts);
+				if (tmessage) {
+					rocketMsgObj.tmid = tmessage._id;
+				}
+			}
 			if (slackMessage.subtype === 'bot_message') {
 				rocketUser = Users.findOneById('rocket.cat', { fields: { username: 1 } });
 			}

app/slackbridge/server/SlackAdapter.js

@@ -667,6 +667,13 @@ export default class SlackAdapter {
 				icon_url: iconUrl,
 				link_names: 1,
 			};
+
+			if (rocketMessage.tmid) {
+				const tmessage = Messages.findOneById(rocketMessage.tmid);
+				if (tmessage && tmessage.slackTs) {
+					data.thread_ts = tmessage.slackTs;
+				}
+			}
 			logger.slack.debug('Post Message To Slack', data);
 
 			// If we don't have the bot id yet and we have multiple slack bridges, we need to keep track of the messages that are being sent