CPS-1526 Fix response message for PATCH operation

- Fixed the Response code and message when trying to update multiple
  data trees at once
- Response code changed to 400
- Since the patch operation across multiple data trees is not
  supported when xpath is set to root node xpath, appropriate message is
  returned in response
- Existing functionality of updating one data node with root node xpath
  remains as it is.
- Updated API documentation and release notes

Issue-ID: CPS-1526
Signed-off-by: arpitsingh <as00745003@techmahindra.com>
Change-Id: I5d25a06bb5d407316ccfb2f85877cbe56a9f6f31
diff --git a/docs/release-notes.rst b/docs/release-notes.rst
index 12e485a..d52e729 100755
--- a/docs/release-notes.rst
+++ b/docs/release-notes.rst
@@ -39,7 +39,7 @@
 Bug Fixes
 ---------
 3.2.6
-    - None
+    - `CPS-1526 <https://jira.onap.org/browse/CPS-1526>`_ Fix response message for PATCH operation
 
 Features
 --------
@@ -229,6 +229,9 @@
 For upgrading, CPS uses Liquibase for database upgrades. CPS/NCMP currently only supports upgrading from Liquibase changelog 11 to Liquibase changelog 16.
 This is from commit CPS-506: List all known modules and revision to CPS-1312: Default CMHandles to READY during upgrade or from ONAP release Honolulu to Kohn.
 
+CPS core Patch operation currently supports updating data of one top level data node. When performing Patch on multiple top level data nodes at once
+a 400 Bad Request is sent as response. This is part of commit CPS-1526.
+
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 ..      * * *   KOHN   * * *
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