refac: several unverified users can exist at once: an empty reset or verification code is stored as no value so it doesn't break the unique constraint, and deleting a user removes the row so the same username and email can register again

internal/infrastructure/persistence/mappers/userMapper.go

@@ -5,15 +5,29 @@ import (
 	"RenewCMS/internal/infrastructure/persistence/models"
 )
 
+func nullableStringToDomain(value *string) string {
+	if value == nil {
+		return ""
+	}
+	return *value
+}
+
+func DomainToNullableString(value string) *string {
+	if value == "" {
+		return nil
+	}
+	return &value
+}
+
 func UserToDomain(m models.User) user.User {
 	return user.User{
 		ID:                     m.ID,
 		Username:               m.Username,
 		Password:               m.Password,
-		PasswordResetCode:      m.PasswordResetCode,
+		PasswordResetCode:      nullableStringToDomain(m.PasswordResetCode),
 		Email:                  m.Email,
 		IsVerified:             m.IsVerified,
-		VerificationCode:       m.VerificationCode,
+		VerificationCode:       nullableStringToDomain(m.VerificationCode),
 		VerificationExpiration: m.VerificationExpiration,
 		CreatedAt:              m.CreatedAt,
 		UpdatedAt:              m.UpdatedAt,
@@ -24,10 +38,10 @@ func UserToModel(a user.User) models.User {
 	return models.User{
 		Username:               a.Username,
 		Password:               a.Password,
-		PasswordResetCode:      a.PasswordResetCode,
+		PasswordResetCode:      DomainToNullableString(a.PasswordResetCode),
 		Email:                  a.Email,
 		IsVerified:             a.IsVerified,
-		VerificationCode:       a.VerificationCode,
+		VerificationCode:       DomainToNullableString(a.VerificationCode),
 		VerificationExpiration: a.VerificationExpiration,
 		CreatedAt:              a.CreatedAt,
 		UpdatedAt:              a.UpdatedAt,