[management] Omit proxy_protocol from API response when false (#5656)

The internal Target model uses a plain bool for ProxyProtocol,
which was always serialized to the API response as false even
when not configured. Only set the API field when true so it
gets omitted via omitempty when unset.

management/internals/modules/reverseproxy/service/service.go

@@ -262,7 +262,9 @@ func (s *Service) ToAPIResponse() *api.Service {
 		if opts == nil {
 			opts = &api.ServiceTargetOptions{}
 		}
-		opts.ProxyProtocol = &target.ProxyProtocol
+		if target.ProxyProtocol {
+			opts.ProxyProtocol = &target.ProxyProtocol
+		}
 		st.Options = opts
 		apiTargets = append(apiTargets, st)
 	}