fix(graphql-server): attach the notify client's error handler before the LISTEN

[pyramation]

Summary

Fixes constructive-io/constructive-planning#1605: graphql-public exits on Error: Connection terminated unexpectedly emitted on a Client with no error listener, taking every GraphQL host down until Kubernetes restarts the pod.

listenForChanges issued LISTEN "schema:update" before attaching the error handler, so between pool checkout and that client.on('error', …) the client was unguarded — and Node rethrows an unlistened error event. The window is re-entered on every reconnect (the error handler itself calls addEventListener()), so a flapping Postgres gets repeated chances to kill the process.

 this.listenClient = client;
 this.listenRelease = release;
+client.on('error', (e) => this.dropListener(client, 'Error with database notify listener', e));
 client.on('notification', …);
-client.query('LISTEN "schema:update"');
-client.on('error', …);
+client.query('LISTEN "schema:update"').catch((e) => this.dropListener(client, 'Failed to LISTEN for schema:update', e));

Teardown moved into dropListener(client, message, err), which no-ops unless this.listenClient === client — so a second failure (or one racing shutdown/removeEventListener) cannot double-release or spawn a second reconnect chain. Reconnect/log/release behavior is otherwise unchanged.

Also addresses the second half of the issue: the LISTEN was fire-and-forget, so a failed LISTEN left the server believing it was watching schema:update while schema changes silently stopped propagating. It now reconnects through the same path.

Test plan

New graphql/server-test/__tests__/notify-listener.test.ts (no database needed — fake PoolClient) asserts: an error listener is present at the moment query() is called, a dropped connection releases + reconnects exactly once, repeated failures tear down once, and a rejected LISTEN reconnects.

Link to Devin session: https://app.devin.ai/sessions/acb0555695da4f628f32371a9a93dc02
Requested by: @pyramation

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring