Schema: convert dashboards from v1beta1 to v2beta1 (#109037)

- Implement full conversion pipeline from v1beta1 → v2beta1
- Ensure frontend–backend parity for all dashboard serialization paths
- Add automatic data loss detection for conversions (panels, queries, annotations, links, variables)
- Extract atomic conversion functions for v0 → v1beta1 → v2alpha1 → v2beta1
- Introduce conversion metrics and detailed logging for loss tracking
- Normalize datasource resolution, defaults, and annotation processing
- Improve panel layout serialization and y-coordinate normalization
- Fix inconsistencies in nested panels and collapsed row behavior
- Refine variable handling:
  - Filter refId from variable query specs
  - Default variable refresh to 'never' (matches frontend)
  - Fix constant and interval variable handling for missing queries
- Unify schema defaults (enable, hide, iconColor, editable, liveNow)
- Fix pluginId usage (UID vs type) and datasource references
- Fix metrics.go bug swallowing errors (return nil → return err)
- Add tests for version-specific conversion error handling
- Add data loss detection tests using source/target version comparison
- Clean up lint issues, legacy code, and redundant files
- Update OpenAPI snapshots and migrated dashboards
- Improve backend migrator to reuse datasource provider and match frontend logic

Co-authored-by: Haris Rozajac <haris.rozajac12@gmail.com>
Co-authored-by: Oscar Kilhed <oscar.kilhed@grafana.com>
Co-authored-by: Stephanie Hingtgen <stephanie.hingtgen@grafana.com>

apps/dashboard/pkg/migration/migrate.go

@@ -13,11 +13,20 @@ func Initialize(dsInfoProvider schemaversion.DataSourceInfoProvider) {
 	migratorInstance.init(dsInfoProvider)
 }
 
+// GetDataSourceInfoProvider returns the datasource info provider instance that was initialized.
+// This allows reuse of the same provider instance across migrations and conversions.
+func GetDataSourceInfoProvider() schemaversion.DataSourceInfoProvider {
+	// Wait for initialization to complete
+	<-migratorInstance.ready
+	return migratorInstance.dsInfoProvider
+}
+
 // ResetForTesting resets the migrator singleton for testing purposes.
 func ResetForTesting() {
 	migratorInstance = &migrator{
-		migrations: map[int]schemaversion.SchemaVersionMigrationFunc{},
-		ready:      make(chan struct{}),
+		migrations:     map[int]schemaversion.SchemaVersionMigrationFunc{},
+		ready:          make(chan struct{}),
+		dsInfoProvider: nil,
 	}
 	initOnce = sync.Once{}
 }
@@ -37,12 +46,14 @@ var (
 )
 
 type migrator struct {
-	ready      chan struct{}
-	migrations map[int]schemaversion.SchemaVersionMigrationFunc
+	ready          chan struct{}
+	migrations     map[int]schemaversion.SchemaVersionMigrationFunc
+	dsInfoProvider schemaversion.DataSourceInfoProvider
 }
 
 func (m *migrator) init(dsInfoProvider schemaversion.DataSourceInfoProvider) {
 	initOnce.Do(func() {
+		m.dsInfoProvider = dsInfoProvider
 		m.migrations = schemaversion.GetMigrations(dsInfoProvider)
 		close(m.ready)
 	})