refactor: reorganize packages into a domain-based layered structure

internal/account/repo.go

@@ -0,0 +1,50 @@
+package account
+
+import (
+	"gorm.io/gorm"
+)
+
+type UserRepository struct {
+	db *gorm.DB
+}
+
+func NewUserRepository(db *gorm.DB) *UserRepository {
+	return &UserRepository{db: db}
+}
+
+func (ur *UserRepository) CreateUser(user *User) error {
+	if err := ur.db.Create(user).Error; err != nil {
+		return err
+	}
+	return nil
+}
+
+func (ur *UserRepository) RenameByID(id uint, newUsername string) error {
+	if err := ur.db.Model(&User{}).Where("id = ?", id).Update("username", newUsername).Error; err != nil {
+		return err
+	}
+	return nil
+}
+
+func (ur *UserRepository) ChangePassword(id uint, newPassword string) error {
+	if err := ur.db.Model(&User{}).Where("id = ?", id).Update("password", newPassword).Error; err != nil {
+		return err
+	}
+	return nil
+}
+
+func (ur *UserRepository) FindByID(id uint) (*User, error) {
+	var user User
+	if err := ur.db.First(&user, id).Error; err != nil {
+		return nil, err
+	}
+	return &user, nil
+}
+
+func (ur *UserRepository) FindByUsername(username string) (*User, error) {
+	var user User
+	if err := ur.db.Where("username = ?", username).First(&user).Error; err != nil {
+		return nil, err
+	}
+	return &user, nil
+}