Add zones ownership transfer request to Designate tempest plugin

This patch adds zone transfer_request_client's methods and tests
to Designate tempest plugin.

Partially-Implements: blueprint designate-tempest-plugin

Change-Id: I0c5b4a5796c398fb1d24cde124203c865ea21833
diff --git a/designate_tempest_plugin/data_utils.py b/designate_tempest_plugin/data_utils.py
index 448095e..ae2b1a7 100644
--- a/designate_tempest_plugin/data_utils.py
+++ b/designate_tempest_plugin/data_utils.py
@@ -216,3 +216,20 @@
         "name": rand_zone_name(prefix='tld', suffix='')
     }
     return data
+
+
+def rand_transfer_request_data(description=None, target_project_id=None):
+    """Generate random transfer request data, with optional overrides
+
+    :return: A TransferRequest data
+    """
+
+    data = {}
+
+    if description is None:
+        data['description'] = data_utils.rand_name(prefix='Description ')
+
+    if target_project_id:
+        data['target_project_id'] = target_project_id
+
+    return data