fix(validation): correct CustomValidator and strutils.Parser handling, add tests

internal/serialization/validation_common_test.go

@@ -0,0 +1,34 @@
+package serialization
+
+import (
+	"testing"
+
+	"github.com/go-playground/validator/v10"
+)
+
+// Common helper functions
+func ptr[T any](s T) *T {
+	return &s
+}
+
+// Common test function for MustRegisterValidation
+func TestMustRegisterValidation(t *testing.T) {
+	// Test registering a custom validation
+	fn := func(fl validator.FieldLevel) bool {
+		return fl.Field().String() != "invalid"
+	}
+
+	// This should not panic
+	MustRegisterValidation("test_tag", fn)
+
+	// Verify the validation was registered
+	err := validate.VarWithValue("valid", "test", "test_tag")
+	if err != nil {
+		t.Errorf("Expected validation to pass, got error: %v", err)
+	}
+
+	err = validate.VarWithValue("invalid", "test", "test_tag")
+	if err == nil {
+		t.Error("Expected validation to fail")
+	}
+}