feat: enable auto migration based on resource count (#115619)

* feat(unified): migration at startup based on resource count

-- draft

* feat: introduce auto migration enablement for dashboards & folders

* feat: enable auto migration based on threshold

* fix: improve

* fix: pass in the auto migrate per migration definition

* fix: minor

* fix: only use one options

* fix: test

* fix: test

* fix: tests

* fix: simplify configs

* chore: rename

* fix: add integration test

* fix: add integration test

* fix: integration tests

* chore: add comments

* fix: address comment

* fix: address comments

* fix: test and auto migration flow

* fix: test

---------

Co-authored-by: Rafael Paulovic <rafael.paulovic@grafana.com>

pkg/setting/setting.go

@@ -637,6 +637,8 @@ type UnifiedStorageConfig struct {
 	// EnableMigration indicates whether migration is enabled for the resource.
 	// If not set, will use the default from MigratedUnifiedResources.
 	EnableMigration bool
+	// AutoMigrationThreshold is the threshold below which a resource is automatically migrated.
+	AutoMigrationThreshold int
 }
 
 type InstallPlugin struct {