Add user management

backend/app/models/user.go

@@ -0,0 +1,51 @@
+package models
+
+import "errors"
+
+type User struct {
+	ID             string `json:"id"`
+	Name           string `json:"name"`
+	Role           string `json:"role"`
+	HashedPassword string `json:"hashed_password"`
+	CreatedAt      string `json:"created_at"`
+}
+
+type CreateUserRequest struct {
+	Name     string `json:"name"`
+	Role     string `json:"role"`
+	Password string `json:"password"`
+}
+
+func ValidateCreateUserRequest(req *CreateUserRequest) error {
+	if req.Name == "" {
+		return errors.New("name is required")
+	}
+	if req.Role == "" {
+		return errors.New("role is required")
+	}
+	if req.Role != "admin" && req.Role != "user" {
+		return errors.New("role must be either 'admin' or 'user'")
+	}
+	if req.Password == "" {
+		return errors.New("password is required")
+	}
+	return nil
+}
+
+type UpdateUserRequest struct {
+	Name string `json:"name"`
+	Role string `json:"role"`
+}
+
+func ValidateUpdateUserRequest(req *UpdateUserRequest) error {
+	if req.Name == "" {
+		return errors.New("name is required")
+	}
+	if req.Role == "" {
+		return errors.New("role is required")
+	}
+	if req.Role != "admin" && req.Role != "user" {
+		return errors.New("role must be either 'admin' or 'user'")
+	}
+	return nil
+}