feat(dashboards): Make organizations non-nullable (#93033)

This is a follow up to #92272 where I added the column as nullable and a
backfill PR to update preexisting models. New instances are always
created with the organization, and I've run the backfill PR across all
deployments.

Closes DAIN-535

Author: narsaynorath

migrations_lockfile.txt

@@ -23,7 +23,7 @@ preprod: 0001_emerge_upload_models
 
 replays: 0001_squashed_0005_drop_replay_index
 
-sentry: 0923_dashboard_starred_backfill_orgs
+sentry: 0924_dashboard_add_unique_constraint_for_user_org_position
 
 social_auth: 0001_squashed_0002_default_auto_field
 

src/sentry/migrations/0924_dashboard_add_unique_constraint_for_user_org_position.py

@@ -0,0 +1,44 @@
+# Generated by Django 5.2.1 on 2025-06-06 15:48
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+import sentry.db.models.fields.foreignkey
+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", "0923_dashboard_starred_backfill_orgs"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="dashboardfavoriteuser",
+            name="organization",
+            field=sentry.db.models.fields.foreignkey.FlexibleForeignKey(
+                on_delete=django.db.models.deletion.CASCADE, to="sentry.organization"
+            ),
+        ),
+        migrations.AddConstraint(
+            model_name="dashboardfavoriteuser",
+            constraint=models.UniqueConstraint(
+                fields=("user_id", "organization_id", "position"),
+                name="sentry_dashboardfavoriteuser_user_id_organization_id_position_uniq",
+            ),
+        ),
+    ]

src/sentry/models/dashboard.py

@@ -35,7 +35,7 @@ class DashboardFavoriteUser(DefaultFieldsModel):
     __relocation_scope__ = RelocationScope.Organization
 
     user_id = HybridCloudForeignKey("sentry.User", on_delete="CASCADE")
-    organization = FlexibleForeignKey("sentry.Organization", null=True)
+    organization = FlexibleForeignKey("sentry.Organization")
     dashboard = FlexibleForeignKey("sentry.Dashboard", on_delete=models.CASCADE)
 
     position = models.PositiveSmallIntegerField(null=True)
@@ -49,6 +49,11 @@ class Meta:
                 fields=["user_id", "dashboard"],
                 name="sentry_dashboardfavoriteuser_user_id_dashboard_id_2c7267a5_uniq",
             ),
+            # A user can only have one starred dashboard in a specific position
+            UniqueConstraint(
+                fields=["user_id", "organization_id", "position"],
+                name="sentry_dashboardfavoriteuser_user_id_organization_id_position_uniq",
+            ),
         ]