refactor/checkout (#8)

Co-authored-by: matst80 <mats.tornberg@gmail.com>
Reviewed-on: #8
Co-authored-by: Mats Törnberg <mats@tornberg.me>
Co-committed-by: Mats Törnberg <mats@tornberg.me>

pkg/actor/mutation_registry.go

@@ -95,14 +95,18 @@ type MutationHandler interface {
 type RegisteredMutation[V any, T proto.Message] struct {
 	name    string
 	handler func(*V, T) error
-	create  func() T
+	create  func() proto.Message
 	msgType reflect.Type
 }
 
-func NewMutation[V any, T proto.Message](handler func(*V, T) error, create func() T) *RegisteredMutation[V, T] {
+func NewMutation[V any, T proto.Message](handler func(*V, T) error) *RegisteredMutation[V, T] {
 	// Derive the name and message type from a concrete instance produced by create().
 	// This avoids relying on reflect.TypeFor (which can yield unexpected results in some toolchains)
 	// and ensures we always peel off the pointer layer for proto messages.
+	create := func() proto.Message {
+		m := new(T)
+		return *m
+	}
 	instance := create()
 	rt := reflect.TypeOf(instance)
 	if rt.Kind() == reflect.Ptr {