add id getter for processors

internal/processor/test/string-create_test.go

@@ -16,6 +16,7 @@ func TestStringCreateFromRegistry(t *testing.T) {
 	}
 
 	processorInstance, err := registration.New(config.ProcessorConfig{
+		Id:   "test-id",
 		Type: "string.create",
 		Params: map[string]any{
 			"template": "{{.Payload}}",
@@ -25,6 +26,10 @@ func TestStringCreateFromRegistry(t *testing.T) {
 		t.Fatalf("failed to create string.create processor: %s", err)
 	}
 
+	if processorInstance.Id() != "test-id" {
+		t.Fatalf("string.create processor has wrong id: %s", processorInstance.Id())
+	}
+
 	if processorInstance.Type() != "string.create" {
 		t.Fatalf("string.create processor has wrong type: %s", processorInstance.Type())
 	}