Rename db files to match model names

- users.go -> virtual_users.go
- domains.go -> virtual_domains.go
- aliases.go -> virtual_aliases.go

backend/internal/db/virtual_domains.go

@@ -0,0 +1,68 @@
+package db
+
+func (d *DB) GetAllDomains() ([]DomainStats, error) {
+	var domains []VirtualDomain
+	if err := d.Order("name ASC").Find(&domains).Error; err != nil {
+		return nil, err
+	}
+
+	stats := make([]DomainStats, len(domains))
+	for i, dom := range domains {
+		var userCount, aliasCount int64
+		d.Model(&VirtualUser{}).Where("domain_id = ?", dom.ID).Count(&userCount)
+		d.Model(&VirtualAlias{}).Where("domain_id = ?", dom.ID).Count(&aliasCount)
+
+		stats[i] = DomainStats{
+			ID:         dom.ID,
+			Name:       dom.Name,
+			UserCount:  userCount,
+			AliasCount: aliasCount,
+		}
+	}
+
+	if stats == nil {
+		stats = []DomainStats{}
+	}
+	return stats, nil
+}
+
+func (d *DB) GetDomainByID(id uint) (*VirtualDomain, error) {
+	var domain VirtualDomain
+	if err := d.Where("id = ?", id).First(&domain).Error; err != nil {
+		return nil, err
+	}
+	return &domain, nil
+}
+
+func (d *DB) GetDomainByName(name string) (*VirtualDomain, error) {
+	var domain VirtualDomain
+	if err := d.Where("name = ?", name).First(&domain).Error; err != nil {
+		return nil, err
+	}
+	return &domain, nil
+}
+
+func (d *DB) CreateDomain(name string) (*VirtualDomain, error) {
+	domain := VirtualDomain{Name: name}
+	if err := d.Create(&domain).Error; err != nil {
+		return nil, err
+	}
+	return &domain, nil
+}
+
+func (d *DB) DeleteDomain(id uint) error {
+	tx := d.Begin()
+	defer func() { tx.Rollback() }()
+
+	if err := tx.Where("domain_id = ?", id).Delete(&VirtualUser{}).Error; err != nil {
+		return err
+	}
+	if err := tx.Where("domain_id = ?", id).Delete(&VirtualAlias{}).Error; err != nil {
+		return err
+	}
+	if err := tx.Delete(&VirtualDomain{}, id).Error; err != nil {
+		return err
+	}
+
+	return tx.Commit().Error
+}