fix(sentry_apps): Defer resource change webhooks until transaction commit

[sentry]

This PR addresses the RetryTaskError occurring in sentry.sentry_apps.tasks.sentry_apps.process_resource_change_bound.

Problem:
The process_resource_change_bound task, responsible for sending webhooks on resource changes (like Group creation), was sometimes failing with Group.DoesNotExist. This happened because the task was enqueued and executed before the database transaction that created the Group had fully committed.

Root Cause:
A race condition existed where the task worker would pick up and attempt to process the webhook task before the corresponding Group record was durably written to the database. When the task tried to fetch the Group using model.objects.get(id=instance_id), it would not find the record, leading to a Group.DoesNotExist exception and subsequent task retries.

Solution:
To resolve this, django.db.transaction.on_commit() has been introduced. The calls to process_resource_change_bound.delay() within process_resource_change_bounds() are now wrapped with transaction.on_commit(). This ensures that the webhook tasks are only added to the queue after the current database transaction has successfully committed. By guaranteeing the Group exists in the database before the task is even queued, we eliminate the race condition and prevent the Group.DoesNotExist errors.

The existing retry mechanism on process_resource_change_bound remains in place to handle any other legitimate transient failures.

Legal Boilerplate

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