feat(storage): Add samples related to AppendableObject and OpenObject (#15563)

Author: shubham-up-47

google/cloud/storage/async/client.h

@@ -371,7 +371,7 @@ class AsyncClient {
       std::int64_t limit, Options opts = {});
 
   /*
-  [start-appendable-object-upload]
+  [create-and-write-appendable-object]
   Initiates a [resumable upload][resumable-link] for an appendable object.
 
   Appendable objects allow you to create an object and upload data to it
@@ -385,21 +385,21 @@ class AsyncClient {
   closure of the streaming RPC used for the upload.
 
   @par Example
-  @snippet storage_async_samples.cc start-appendable-object-upload
+  @snippet storage_async_samples.cc create-and-write-appendable-object
 
   @par Idempotency
   This function is always treated as idempotent, and the library will
   automatically retry the function on transient errors.
 
   [resumable-link]: https://cloud.google.com/storage/docs/resumable-uploads
-  [start-appendable-object-upload]
+  [create-and-write-appendable-object]
   */
 
   /**
    * Starts a new resumable upload session for appendable objects and
    * automatic recovery from transient failures.
    *
-   * @snippet{doc} async/client.h start-appendable-object-upload
+   * @snippet{doc} async/client.h create-and-write-appendable-object
    *
    * @param bucket_name the name of the bucket that contains the object.
    * @param object_name the name of the object to be uploaded.
@@ -414,7 +414,7 @@ class AsyncClient {
    * Starts a new resumable upload session for appendable objects and
    * automatic recovery from transient failures.
    *
-   * @snippet{doc} async/client.h start-appendable-object-upload
+   * @snippet{doc} async/client.h create-and-write-appendable-object
    *
    * @param request the request contents, it must include the bucket name and
    *     object name. Many other fields are optional.