fixed gorm shema for correct deletion and many2many relation beetween users and devices

server/internal/db/db.go

@@ -16,5 +16,6 @@ func AutoMigrate(db *gorm.DB) error {
 		&models.User{},
 		&models.Device{},
 		&models.Record{},
+		&models.UserDevice{},
 	)
 }

server/internal/handlers/users.go

@@ -106,12 +106,10 @@ func (h *UsersHandler) Delete(c *gin.Context) {
 		return
 	}
 	var u models.User
-	if err := h.db.Preload("Devices").First(&u, id).Error; err != nil {
+	if err := h.db.First(&u, id).Error; err != nil {
 		c.JSON(http.StatusNotFound, gin.H{"error": "user not found"})
 		return
 	}
-	// optional safeguard: prevent self-delete; uncomment if desired
-	// if ClaimUserID(MustClaims(c)) == u.ID { c.JSON(http.StatusBadRequest, gin.H{"error":"cannot delete yourself"}); return }
 	if err := h.db.Transaction(func(tx *gorm.DB) error {
 		if err := tx.Model(&u).Association("Devices").Clear(); err != nil {
 			return err

server/internal/models/device.go

@@ -5,7 +5,7 @@ import "time"
 type Device struct {
 	GUID      string   `gorm:"primaryKey"`
 	Name      string   `gorm:"size:255;not null"`
-	Users     []User   `gorm:"many2many:user_devices;joinForeignKey:ID;joinReferences:GUID"`
+	Users     []User   `gorm:"many2many:user_devices;constraint:OnDelete:CASCADE;"`
 	Records   []Record `gorm:"foreignKey:DeviceGUID;references:GUID;constraint:OnDelete:CASCADE"`
 	CreatedAt time.Time
 	UpdatedAt time.Time

server/internal/models/user.go

@@ -14,7 +14,7 @@ type User struct {
 	Username  string   `gorm:"uniqueIndex;size:255;not null"`
 	Password  string   `gorm:"not null"`
 	Role      Role     `gorm:"type:varchar(16);not null;default:'user'"`
-	Devices   []Device `gorm:"many2many:user_devices;joinForeignKey:ID;joinReferences:GUID"`
+	Devices   []Device `gorm:"many2many:user_devices;constraint:OnDelete:CASCADE;"`
 	CreatedAt time.Time
 	UpdatedAt time.Time
 }

server/internal/models/user_device.go

@@ -0,0 +1,13 @@
+package models
+
+import "time"
+
+type UserDevice struct {
+	UserID     uint   `gorm:"primaryKey;index;not null"`
+	DeviceGUID string `gorm:"primaryKey;size:64;index;not null"`
+	CreatedAt  time.Time
+
+	// Optional FKs with cascade (you already have cascade constraints on both sides)
+	User   User   `gorm:"constraint:OnDelete:CASCADE;"`
+	Device Device `gorm:"constraint:OnDelete:CASCADE;foreignKey:DeviceGUID;references:GUID"`
+}