this commit is refactoring the function ngap_gNB_handle_nas_first_req to (1) fill first a local instance of ngap_gNB_ue_context_t and then (2) pass it to ngap_store_ue_context which will allocate memory for the instance to store in ngap
this commit is refactoring the function ngap_gNB_handle_nas_first_req to (1) fill first a local instance of ngap_gNB_ue_context_t and then (2) pass it to ngap_store_ue_context which will allocate memory for the instance to store in ngap