SOL002 VNF Performance Management - Implementation of deltas between v3.3.1 and v2.7.1

This merge request refers to the implementation of deltas between v3.3.1 and v2.7.1 of SOL002 VNF Performance Management Interface.

@lynchpi @aelken @matsuurat @carignani @sayama @kraja @zulfiqar @zafar

**Deadline for review: Wednesday 3rd March 2021 @6pm CET

Review period elapsed: approved**

SOL002/VNFPerformanceManagement-API/environment/variables.txt

@@ -9,6 +9,7 @@ ${apiName}        vnfpm
 
 
 ${CONTENT_TYPE_JSON}    application/json
+${CONTENT_TYPE_PATCH}    application/merge-patch+json
 ${ACCEPT_JSON}    application/json
 ${NEG_AUTHORIZATION}    Bearer negativetoken
 ${FIELD_USAGE}    1
@@ -18,6 +19,8 @@ ${AUTH_USAGE}    1
 ${VNFM_DUPLICATION}    1
 ${VNFM_CHECKS_NOTIF_ENDPOINT}    1
 ${callback_uri}    http://localhost
+${unreachable_callback_uri}    http://not-reachable-uri
+${new_callback_uri}    http://newcallbackuri-for-PMJobModifications
 ${callback_port}    9091
 ${callback_endpoint}    /endpoint
 ${callback_endpoint_error}    /endpoint_404