Create NS NBI support

• Preconditions: 
  • SOL007 NS packages are stored in ETSI Catalog Manager.
  • the Cli-based SO NFVO Client is ready to send the SOL005-compliant Create NS request
  • The SO-NFVO (so-etsi-nfvo) pod is ready

• Support the SOL005-compliant Create NS API 
  • Supports Create NS request API: POST /api/nslcm/v1/ns_instances (CreateNsRequest)
  • Supports Create NS responses with NsInstance with 201 (for success) or an error
    • Returns a dummy 201 until the backend business logic is ready 
    • Only mandatory attributes of NsInstance will be set.
    • Support successful or error conditions
  • Sends NsIdentifierCreationNotification to the NFVO subscriber(s) (e.g., ONAP SO SOL005 Adapter)
    • Note: this will be handled by the separate user story: Sends NsIdentifierCreationNotification to the NFVO subscriber(s) (e.g., ONAP SO SOL005 Adapter)

• Post conditions: the NS Instance is set as NOT_INSTANTIATED state

Note: secure communication is handled by a separate user story, SO-3165.