added new ddm service metadata

otc_metadata/data/services.yaml

@@ -214,6 +214,22 @@ documents:
     service_type: dcs
     title: User Guide
     type: umn
+  - hc_location: api/ddm
+    html_location: docs/ddm/api-ref
+    link: /distributed-database-middleware/api-ref/
+    pdf_name: ddm-api-ref
+    rst_location: api-ref/source
+    service_type: ddm
+    title: API Reference
+    type: api-ref
+  - hc_location: usermanual/ddm
+    html_location: docs/ddm/umn
+    link: /distributed-database-middleware/umn/
+    pdf_name: ddm-umn
+    rst_location: umn/source
+    service_type: ddm
+    title: User Guide
+    type: umn
   - hc_location: api/dds
     html_location: docs/dds/api-ref
     link: /document-database-service/api-ref/