add uniqueness validation to Service
add uniqueness validation to Service

a service with the same port and proto cannot exist
for the same host_id now.

MSP-11643

farias-r7/metasploit_data_models,rapid7/metasploit_data_models,rapid7/metasploit_data_models,bcook-r7/metasploit_data_models,bcook-r7/metasploit_data_models,farias-r7/metasploit_data_models,bcook-r7/metasploit_data_models,farias-r7/metasploit_data_models,rapid7/metasploit_data_models