fix: move triggering actions out of transations (#3215)

When removing failing connection in SlackService, we used to trigger
actions in the middle of a db transaction that is locking rows. We also
do all sort of async operations like logging. If the actions for
instance are experiencing any kind of issue, the transaction is kept
open and waiting until the actions times out or the db cancels the
transaction, holding the db connection during all this time.
This commits moves the actual sending of the Slack notification after
the db has been updated. We run into the risk of updating the db and not
sending the notification but we cannot currently guarantee those
operations to be fully atomic without potentially locking the db for a
very long time.
There might be a possibility to now reduce the transaction into a single
atomic query but I didn't want this change to be too heavy right before
the holidays

packages/shared/lib/services/notification/slack.service.ts

@@ -596,7 +596,7 @@ export class SlackService {
         environment_id: number;
         provider: string;
     }): Promise<void> {
-        await db.knex.transaction(async (trx) => {
+        const update = await db.knex.transaction(async (trx) => {
             const slackNotificationsEnabled = await environmentService.getSlackNotificationsEnabled(nangoConnection.environment_id);
             if (!slackNotificationsEnabled) {
                 return;
@@ -638,7 +638,15 @@ export class SlackService {
                     connection_list,
                     updated_at: new Date()
                 });
+            return {
+                id,
+                slackTimestamp: slack_timestamp,
+                adminSlackTimestamp: admin_slack_timestamp,
+                connectionCount: connection_list.length
+            };
+        });
 
+        if (update) {
             // we report resolution to the slack channel which could be either
             // 1) The slack notification is resolved, connection_list === 0
             // 2) The list of failing connections has been decremented
@@ -649,11 +657,11 @@ export class SlackService {
                 originalActivityLogId,
                 environment_id,
                 provider,
-                slack_timestamp as string,
-                admin_slack_timestamp as string,
-                connection_list.length
+                update.slackTimestamp as string,
+                update.adminSlackTimestamp as string,
+                update.connectionCount
             );
-        });
+        }
     }
 
     async closeAllOpenNotificationsForEnv(environment_id: number): Promise<void> {