Added test for go_live_user and go_live_at in the response for get_service_by_id

app/schemas.py

@@ -210,6 +210,7 @@ class ServiceSchema(BaseSchema):
     organisation = field_for(models.Service, 'organisation')
     override_flag = False
     letter_contact_block = fields.Method(serialize="get_letter_contact")
+    go_live_at = field_for(models.Service, 'go_live_at', format='%Y-%m-%d %H:%M:%S.%f')
 
     def get_letter_logo_filename(self, service):
         return service.letter_branding and service.letter_branding.filename