Add keystone unified limits client

Change-Id: If58d8474cae95b1be3044bd52010b8288a7f5fcc
diff --git a/releasenotes/notes/limits-client-d656f16a3d3e84fc.yaml b/releasenotes/notes/limits-client-d656f16a3d3e84fc.yaml
new file mode 100644
index 0000000..311eca3
--- /dev/null
+++ b/releasenotes/notes/limits-client-d656f16a3d3e84fc.yaml
@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Add a new client for keystone's unified limits API to create and update limits.