feat: Introduce Nullable type for optional fields and update user DTOs accordingly

backend/internal/api/handlers/user_handler.go

@@ -182,12 +182,17 @@ func (h *UserHandler) UpdateUser(c *gin.Context) {
 		update.Role = userUpdateDTO.Role
 	}
 	if userUpdateDTO.CompanyID != nil {
-		companyID, err := models.ULIDWrapperFromString(*userUpdateDTO.CompanyID)
-		if err != nil {
-			utils.BadRequestResponse(c, "Invalid company ID format")
-			return
+		if userUpdateDTO.CompanyID.Valid {
+			companyID, err := models.ULIDWrapperFromString(*userUpdateDTO.CompanyID.Value)
+			if err != nil {
+				utils.BadRequestResponse(c, "Invalid company ID format")
+				return
+			}
+			update.CompanyID = &companyID
+		} else {
+			update.CompanyID = nil
+
 		}
-		update.CompanyID = &companyID
 	}
 	if userUpdateDTO.HourlyRate != nil {
 		update.HourlyRate = userUpdateDTO.HourlyRate
@@ -393,8 +398,8 @@ func convertUserToDTO(user *models.User) dto.UserDto {
 
 func convertCreateDTOToModel(dto dto.UserCreateDto) models.UserCreate {
 	var companyID models.ULIDWrapper
-	if dto.CompanyID != nil {
-		companyID, _ = models.ULIDWrapperFromString(*dto.CompanyID) // Ignoring error, validation happens in the model
+	if dto.CompanyID != nil && dto.CompanyID.Valid {
+		companyID, _ = models.ULIDWrapperFromString(*dto.CompanyID.Value) // Ignoring error, validation happens in the model
 	}
 
 	return models.UserCreate{

backend/internal/dtos/helper/nullstring.go

@@ -1,4 +1,4 @@
-package dto
+package helper
 
 import "encoding/json"
 

backend/internal/dtos/user_dto.go

@@ -2,6 +2,8 @@ package dto
 
 import (
 	"time"
+
+	"github.com/timetracker/backend/internal/types"
 )
 
 type UserDto struct {
@@ -16,21 +18,21 @@ type UserDto struct {
 }
 
 type UserCreateDto struct {
-	Email      string  `json:"email" example:"test@example.com"`
-	Password   string  `json:"password" example:"password123"`
-	Role       string  `json:"role" example:"admin"`
-	CompanyID  *string `json:"companyId" example:"01HGW2BBG0000000000000000"`
-	HourlyRate float64 `json:"hourlyRate" example:"50.00"`
+	Email      string                  `json:"email" example:"test@example.com"`
+	Password   string                  `json:"password" example:"password123"`
+	Role       string                  `json:"role" example:"admin"`
+	CompanyID  *types.Nullable[string] `json:"companyId" example:"01HGW2BBG0000000000000000"`
+	HourlyRate float64                 `json:"hourlyRate" example:"50.00"`
 }
 
 type UserUpdateDto struct {
-	ID           string     `json:"id" example:"01HGW2BBG0000000000000000"`
-	CreatedAt    *time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
-	UpdatedAt    *time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
-	LastEditorID *string    `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
-	Email        *string    `json:"email" example:"test@example.com"`
-	Password     *string    `json:"password" example:"password123"`
-	Role         *string    `json:"role" example:"admin"`
-	CompanyID    *string    `json:"companyId" example:"01HGW2BBG0000000000000000"`
-	HourlyRate   *float64   `json:"hourlyRate" example:"50.00"`
+	ID           string                  `json:"id" example:"01HGW2BBG0000000000000000"`
+	CreatedAt    *time.Time              `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    *time.Time              `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID *string                 `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	Email        *string                 `json:"email" example:"test@example.com"`
+	Password     *string                 `json:"password" example:"password123"`
+	Role         *string                 `json:"role" example:"admin"`
+	CompanyID    *types.Nullable[string] `json:"companyId" example:"01HGW2BBG0000000000000000"`
+	HourlyRate   *float64                `json:"hourlyRate" example:"50.00"`
 }

backend/internal/types/nullable.go

@@ -0,0 +1,48 @@
+package types
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// Nullable[T] - Generischer Typ für optionale Werte (nullable fields)
+type Nullable[T any] struct {
+	Value *T   // Der tatsächliche Wert (kann nil sein)
+	Valid bool // Gibt an, ob der Wert gesetzt wurde
+}
+
+// NewNullable erstellt eine gültige Nullable-Instanz
+func NewNullable[T any](value T) Nullable[T] {
+	return Nullable[T]{Value: &value, Valid: true}
+}
+
+// Null erstellt eine leere Nullable-Instanz (ungesetzt)
+func Null[T any]() Nullable[T] {
+	return Nullable[T]{Valid: false}
+}
+
+// MarshalJSON - Serialisiert `Nullable[T]` korrekt ins JSON-Format
+func (n Nullable[T]) MarshalJSON() ([]byte, error) {
+	if !n.Valid {
+		return []byte("null"), nil // Wenn nicht valid, dann NULL
+	}
+	return json.Marshal(n.Value) // Serialisiert den tatsächlichen Wert
+}
+
+// UnmarshalJSON - Deserialisiert JSON in `Nullable[T]`
+func (n *Nullable[T]) UnmarshalJSON(data []byte) error {
+	if string(data) == "null" {
+		n.Valid = true // Wert wurde gesetzt, aber auf NULL
+		n.Value = nil  // Explizit NULL setzen
+		return nil
+	}
+
+	var v T
+	if err := json.Unmarshal(data, &v); err != nil {
+		return fmt.Errorf("invalid JSON for Nullable: %w", err)
+	}
+
+	n.Value = &v
+	n.Valid = true
+	return nil
+}