fix: reduce postgres notify messaging

[saikonen]

Reduces Postgres notify messaging on certain tables by restricting the operations that table triggers are triggered on.

• run/task tables: INSERT only triggers
• metadata table: INSERT only and only for attempt/attempt_ok/code-package/code-package-url metadata entries
• artifact table: disable triggers completely

This PR also changes the heartbeat monitoring to operate on a polling basis, instead of relying on UPDATE triggers from the database

[romain-intel]

Crap -- this was just sitting as pending.

[romain-intel]

I got a tad confused btw -- there seems to be AsyncTaskTablePostgres here but then it is also in ui_backend_service/data/db/tables. Is this normal? Is one used for the metadata service and one for the ui backend. It was a tad confusing because then I wasn't sure which one would get to read operations/conditions, etc for triggers. It's a minor nit but just curious.

[saikonen]

the services/data table classes are functionally aimed for the original metadata services needs. During the ui_backend development introducing new stuff into them was out of scope, and if I recall correctly we did add some changes to existing methods specifically for the UI use case. This is why the ui_backend has its own table classes, that use services/data as a base

there might be some duplication nowadays as the base classes have received some changes as well, but for example keeping the custom queries that the UI relies on out of the base classes made sense back then.

[saikonen]

but then again (to immediately contradict my points), the trigger setup has been kept in the base classes for reasons that I don't recall. Possibly due to some thoughts that the UI backend would initially run off a proper read replica so it would not be able to modify the DB to set up any triggers itself. This ended up not being possible after all due to limitations with read replicas regarding pg_notify, and eventually having the ui_backend be responsible for the trigger setup was the best option.

There is definitely a lot of room for cleanup regarding the table classes.