Separate volume v2 transfers service clients

v2 volume transfers service clients does API calls on
separate resource url "os-volume-transfer" but those
are currently in v2 volumes_client.py.

Each resource service clients should be in separate file.

This commit separate the transfer service client from volumes client
and deprecate the same from volumes service client.

Change-Id: Ia85bcfbadbff4f7c594dc5631ecdd595c5d275f3
diff --git a/releasenotes/notes/volume-transfers-client-e5ed3f5464c0cdc0.yaml b/releasenotes/notes/volume-transfers-client-e5ed3f5464c0cdc0.yaml
new file mode 100644
index 0000000..e5e479b
--- /dev/null
+++ b/releasenotes/notes/volume-transfers-client-e5ed3f5464c0cdc0.yaml
@@ -0,0 +1,18 @@
+---
+features:
+  - |
+    Define volume transfers service clients as libraries.
+    The following volume transfers service clients are defined as library interface.
+
+    * transfers_client(v2)
+deprecations:
+  - |
+    Deprecate volume v2 transfers resource methods from volumes_client(v2) libraries.
+    Same methods are available in new transfers service client: transfers_client(v2)
+    The following methods of volume v2 volumes_clients have been deprecated:
+
+    * create_volume_transfer (v2.volumes_client)
+    * show_volume_transfer (v2.volumes_client)
+    * list_volume_transfers (v2.volumes_client)
+    * delete_volume_transfer (v2.volumes_client)
+    * accept_volume_transfer (v2.volumes_client)