feat(bigquery): support MetadataCacheMode for ExternalDataConfig (#11803)

I skipped integration tests, as this configuration is only supported for BigLake formats.

```
integration_test.go:1761: table.Create: googleapi: Error 400: metadataCacheMode provided for non BigLake external table., invalid
```

Solves #11802

Author: alvarowolfx

bigquery/external.go

@@ -41,6 +41,21 @@ const (
 	Iceberg        DataFormat = "ICEBERG"
 )
 
+// MetadataCacheMode describes the types of metadata cache mode for external data.
+type MetadataCacheMode string
+
+// Constants describing types of metadata cache mode for external data.
+const (
+	// Automatic metadata cache mode triggers automatic background refresh of
+	// metadata cache from the external source. Queries will use the latest
+	// available cache version within the table's maxStaleness interval.
+	Automatic MetadataCacheMode = "AUTOMATIC"
+	// Manual metadata cache mode triggers manual refresh of the
+	// metadata cache from external source. Queries will use the latest manually
+	// triggered cache version within the table's maxStaleness interval.
+	Manual MetadataCacheMode = "MANUAL"
+)
+
 // ExternalData is a table which is stored outside of BigQuery. It is implemented by
 // *ExternalDataConfig.
 // GCSReference also implements it, for backwards compatibility.
@@ -114,6 +129,10 @@ type ExternalDataConfig struct {
 	// When creating an external table, the user can provide a reference file with the table schema.
 	// This is enabled for the following formats: AVRO, PARQUET, ORC.
 	ReferenceFileSchemaURI string
+
+	// Metadata Cache Mode for the table. Set this to
+	// enable caching of metadata from external data source.
+	MetadataCacheMode MetadataCacheMode
 }
 
 func (e *ExternalDataConfig) toBQ() bq.ExternalDataConfiguration {
@@ -127,6 +146,7 @@ func (e *ExternalDataConfig) toBQ() bq.ExternalDataConfiguration {
 		HivePartitioningOptions: e.HivePartitioningOptions.toBQ(),
 		ConnectionId:            e.ConnectionID,
 		ReferenceFileSchemaUri:  e.ReferenceFileSchemaURI,
+		MetadataCacheMode:       string(e.MetadataCacheMode),
 	}
 	if e.Schema != nil {
 		q.Schema = e.Schema.toBQ()
@@ -152,6 +172,7 @@ func bqToExternalDataConfig(q *bq.ExternalDataConfiguration) (*ExternalDataConfi
 		HivePartitioningOptions: bqToHivePartitioningOptions(q.HivePartitioningOptions),
 		ConnectionID:            q.ConnectionId,
 		ReferenceFileSchemaURI:  q.ReferenceFileSchemaUri,
+		MetadataCacheMode:       MetadataCacheMode(q.MetadataCacheMode),
 	}
 	for _, v := range q.DecimalTargetTypes {
 		e.DecimalTargetTypes = append(e.DecimalTargetTypes, DecimalTargetType(v))

bigquery/external_test.go

@@ -99,6 +99,10 @@ func TestExternalDataConfig(t *testing.T) {
 				UseAvroLogicalTypes: true,
 			},
 		},
+		{
+			SourceFormat:      JSON,
+			MetadataCacheMode: Automatic,
+		},
 	} {
 		q := want.toBQ()
 		got, err := bqToExternalDataConfig(&q)

bigquery/table_test.go

@@ -194,13 +194,16 @@ func TestTableMetadataToBQ(t *testing.T) {
 		{&TableMetadata{}, &bq.Table{}},
 		{
 			&TableMetadata{
-				Name:               "n",
-				Description:        "d",
-				Schema:             sc,
-				ExpirationTime:     aTime,
-				Labels:             map[string]string{"a": "b"},
-				ExternalDataConfig: &ExternalDataConfig{SourceFormat: Bigtable},
-				EncryptionConfig:   &EncryptionConfig{KMSKeyName: "keyName"},
+				Name:           "n",
+				Description:    "d",
+				Schema:         sc,
+				ExpirationTime: aTime,
+				Labels:         map[string]string{"a": "b"},
+				ExternalDataConfig: &ExternalDataConfig{
+					SourceFormat:      Bigtable,
+					MetadataCacheMode: Automatic,
+				},
+				EncryptionConfig: &EncryptionConfig{KMSKeyName: "keyName"},
 				ResourceTags: map[string]string{
 					"key1": "val1",
 					"key2": "val2",
@@ -214,10 +217,13 @@ func TestTableMetadataToBQ(t *testing.T) {
 						bqTableFieldSchema("desc", "name", "STRING", "REQUIRED", nil),
 					},
 				},
-				ExpirationTime:            aTimeMillis,
-				Labels:                    map[string]string{"a": "b"},
-				ExternalDataConfiguration: &bq.ExternalDataConfiguration{SourceFormat: "BIGTABLE"},
-				EncryptionConfiguration:   &bq.EncryptionConfiguration{KmsKeyName: "keyName"},
+				ExpirationTime: aTimeMillis,
+				Labels:         map[string]string{"a": "b"},
+				ExternalDataConfiguration: &bq.ExternalDataConfiguration{
+					SourceFormat:      "BIGTABLE",
+					MetadataCacheMode: "AUTOMATIC",
+				},
+				EncryptionConfiguration: &bq.EncryptionConfiguration{KmsKeyName: "keyName"},
 				ResourceTags: map[string]string{
 					"key1": "val1",
 					"key2": "val2",