Add client 'id' to http 409 response

[valedemi]

Please, add client 'id' if client already exist in Create Client Api response.
Without the client ID in response, (the 409 error only returns the customer name) you have to go through a loop to update the master data, with the client ID in response it would be much easier to query the database immediately afterwards with GET /c/{company_id}/entities/clients/{client_id}