feat(bigquery): Add example for creating a external dataset

bigquery/bigquery_create_spanner_external_dataset/main.tf

@@ -0,0 +1,29 @@
+/**
+* Copyright 2024 Google LLC
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*      http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+# [START bigquery_create_spanner_external_dataset]
+resource "google_bigquery_dataset" "default" {
+  dataset_id    = "my_external_dataset"
+  friendly_name = "My external dataset"
+  description   = "This is a test description."
+  location      = "US"
+  external_dataset_reference {
+    # The full identifier of your Spanner database
+    external_source = "google-cloudspanner:/projects/my_project/instances/my_instance/databases/my_database"
+    # Must be empty
+    connection = ""
+  }
+}
+# [END bigquery_create_spanner_external_dataset]