fix(typescript): make SetLabelOptions optional (#766)

* test(bucket): location type system tests
* docs(bucket): add verbiage about deprecated storage classes

src/bucket.ts

@@ -2599,7 +2599,7 @@ class Bucket extends ServiceObject {
 
   setLabels(
     labels: Labels,
-    options: SetLabelsOptions
+    options?: SetLabelsOptions
   ): Promise<SetLabelsResponse>;
   setLabels(labels: Labels, callback: SetLabelsCallback): void;
   setLabels(
@@ -2752,9 +2752,10 @@ class Bucket extends ServiceObject {
    *
    * @see [Storage Classes]{@link https://cloud.google.com/storage/docs/storage-classes}
    *
-   * @param {string} storageClass The new storage class. (`multi_regional`,
-   *     `regional`, `standard`, `nearline`, `coldline`, or
-   *     `durable_reduced_availability`)
+   * @param {string} storageClass The new storage class. (`standard`,
+   *     `nearline`, `coldline`, or `durable_reduced_availability`).
+   *     **Note:** The legacy storage classes `multi_regional` and `regional`
+   *     have been deprecated.
    * @param {object} [options] Configuration options.
    * @param {string} [options.userProject] - The ID of the project which will be
    *     billed for the request.

system-test/storage.ts

@@ -959,6 +959,46 @@ describe('storage', () => {
       assert.strictEqual(metadata.storageClass, 'MULTI_REGIONAL');
     });
 
+    describe('locationType', () => {
+      const types = ['multi-region', 'region', 'dual-region'];
+
+      beforeEach(() => {
+        delete bucket.metadata;
+      });
+
+      it('should be available from getting a bucket', async () => {
+        const [metadata] = await bucket.getMetadata();
+        assert(types.includes(metadata.locationType));
+      });
+
+      it('should be available from creating a bucket', async () => {
+        const [bucket] = await storage.createBucket(generateName());
+        assert(types.includes(bucket.metadata.locationType));
+        return bucket.delete();
+      });
+
+      it('should be available from listing buckets', async () => {
+        const [buckets] = await storage.getBuckets();
+
+        assert(buckets.length > 0);
+
+        buckets.forEach(bucket => {
+          assert(types.includes(bucket.metadata.locationType));
+        });
+      });
+
+      it('should be available from setting retention policy', async () => {
+        await bucket.setRetentionPeriod(RETENTION_DURATION_SECONDS);
+        assert(types.includes(bucket.metadata.locationType));
+        await bucket.removeRetentionPeriod();
+      });
+
+      it('should be available from updating a bucket', async () => {
+        await bucket.setLabels({a: 'b'});
+        assert(types.includes(bucket.metadata.locationType));
+      });
+    });
+
     describe('labels', () => {
       const LABELS = {
         label: 'labelvalue', // no caps or spaces allowed (?)