Fix success response code CM Handle Registration

- changed registartion response code to 204 NO_CONTENT
- improved exception handling for registration API
- fixed failing csit related to changed response code
- updated the release notes for CPS-892 and CPS-837

Issue-ID: CPS-892
Change-Id: I616e340debf1583b058e7ae6b8960972eec00f3e
Signed-off-by: mpriyank <priyank.maheshwari@est.tech>
diff --git a/cps-ncmp-rest/docs/openapi/ncmp-inventory.yml b/cps-ncmp-rest/docs/openapi/ncmp-inventory.yml
index f3f84fe..3cd8e8b 100755
--- a/cps-ncmp-rest/docs/openapi/ncmp-inventory.yml
+++ b/cps-ncmp-rest/docs/openapi/ncmp-inventory.yml
@@ -31,8 +31,8 @@
           schema:
             $ref: 'components.yaml#/components/schemas/RestDmiPluginRegistration'
     responses:
-      201:
-        $ref: 'components.yaml#/components/responses/Created'
+      204:
+        $ref: 'components.yaml#/components/responses/NoContent'
       400:
         $ref: 'components.yaml#/components/responses/BadRequest'
       401: