ref(grouping): Add timestamp to tombstone table (#83473)

This adds a `date_added` field to the `GroupTombstone` table. We currently store who did the tombstoning, and what was tombstoned, but not when it happened. This information would have been helpful in investigating #82501, and while that's now closed, I figured I'd add it in case a similar thing ever comes up again (or in case we want to analyze tombstoning trends over time or something).

Author: lobsterkatie

migrations_lockfile.txt

@@ -15,7 +15,7 @@ remote_subscriptions: 0003_drop_remote_subscription
 
 replays: 0004_index_together
 
-sentry: 0815_add_action_cols_to_threads_model
+sentry: 0816_add_timestamp_to_group_tombstone
 
 social_auth: 0002_default_auto_field
 

src/sentry/migrations/0816_add_timestamp_to_group_tombstone.py

@@ -0,0 +1,34 @@
+# Generated by Django 5.1.4 on 2025-01-15 00:48
+
+import django.utils.timezone
+from django.db import migrations, models
+
+from sentry.new_migrations.migrations import CheckedMigration
+
+
+class Migration(CheckedMigration):
+    # This flag is used to mark that a migration shouldn't be automatically run in production.
+    # This should only be used for operations where it's safe to run the migration after your
+    # code has deployed. So this should not be used for most operations that alter the schema
+    # of a table.
+    # Here are some things that make sense to mark as post deployment:
+    # - Large data migrations. Typically we want these to be run manually so that they can be
+    #   monitored and not block the deploy for a long period of time while they run.
+    # - Adding indexes to large tables. Since this can take a long time, we'd generally prefer to
+    #   run this outside deployments so that we don't block them. Note that while adding an index
+    #   is a schema change, it's completely safe to run the operation after the code has deployed.
+    # Once deployed, run these manually via: https://develop.sentry.dev/database-migrations/#migration-deployment
+
+    is_post_deployment = False
+
+    dependencies = [
+        ("sentry", "0815_add_action_cols_to_threads_model"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="grouptombstone",
+            name="date_added",
+            field=models.DateTimeField(default=django.utils.timezone.now, null=True),
+        ),
+    ]

src/sentry/models/grouptombstone.py

@@ -4,6 +4,7 @@
 from typing import Any
 
 from django.db import models
+from django.utils import timezone
 
 from sentry.backup.scopes import RelocationScope
 from sentry.constants import LOG_LEVELS, MAX_CULPRIT_LENGTH
@@ -23,6 +24,8 @@
 class GroupTombstone(Model):
     __relocation_scope__ = RelocationScope.Excluded
 
+    # Will be null for tombstones created before January 2025
+    date_added = models.DateTimeField(default=timezone.now, null=True)
     previous_group_id = BoundedBigIntegerField(unique=True)
     project = FlexibleForeignKey("sentry.Project")
     level = BoundedPositiveIntegerField(