feat: provide the default stream name

Author: tomrussello

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/StreamWriter.java

@@ -560,6 +560,13 @@ public static void setMaxRequestCallbackWaitTime(Duration waitTime) {
     ConnectionWorker.MAXIMUM_REQUEST_CALLBACK_WAIT_TIME = waitTime;
   }
 
+  /**
+   * @return the default stream name associated with tableName
+   */
+  public static String getDefaultStreamName(TableName tableName) {
+    return tableName + defaultStreamMatching;
+  }
+
   long getCreationTimestamp() {
     return creationTimestamp;
   }

google-cloud-bigquerystorage/src/test/java/com/google/cloud/bigquery/storage/v1/StreamWriterTest.java

@@ -2224,4 +2224,13 @@ public void testExclusiveAppendSuccessAndNonRetryableError() throws Exception {
         Status.Code.INVALID_ARGUMENT,
         ((StatusRuntimeException) ex.getCause()).getStatus().getCode());
   }
+
+  @Test
+  public void testGetDefaultStreamName() {
+    TableName tableName = TableName.of("projectId", "datasetId", "tableId");
+
+    String actualDefaultName = StreamWriter.getDefaultStreamName(tableName);
+
+    assertEquals("projects/projectId/datasets/datasetId/tables/tableId/_default", actualDefaultName);
+  }
 }