chore: replace machine filter with placement constraint in service spec

pkg/api/placement.go

@@ -0,0 +1,8 @@
+package api
+
+// Placement defines the placement constraints for service containers.
+type Placement struct {
+	// Machines is a list of machine names or IDs where service containers are allowed to be deployed.
+	// If empty, containers can be deployed to any available machine in the cluster.
+	Machines []string `json:",omitempty"`
+}

pkg/api/service.go

@@ -42,6 +42,8 @@ type ServiceSpec struct {
 	// Mode is the replication mode of the service. Default is ServiceModeReplicated if empty.
 	Mode string
 	Name string
+	// Placement defines the placement constraints for the service.
+	Placement Placement
 	// Ports defines what service ports to publish to make the service accessible outside the cluster.
 	Ports []PortSpec
 	// Replicas is the number of containers to run for the service. Only valid for a replicated service.