feat: implement repository layer for data access

- Add CertificateRepository with CRUD operations
- Implement CertificateAuthorityRepository for CA management
- Add CertificateRequestRepository for CSR handling
- Include UserRepository and OrganizationRepository
- Implement proper error handling and validation
- Add support for soft deletes and relationships
- Include query optimization and filtering capabilities

repositories/user.go

@@ -0,0 +1,56 @@
+package repositories
+
+import (
+	"git.secnex.io/secnex/certman/models"
+	"gorm.io/gorm"
+)
+
+type UserRepository struct {
+	db *gorm.DB
+}
+
+// NewUserRepository creates a new user repository
+func NewUserRepository(db *gorm.DB) *UserRepository {
+	return &UserRepository{db: db}
+}
+
+// GetByID returns a user by their ID
+func (r *UserRepository) GetByID(id string) (models.User, error) {
+	var user models.User
+	if err := r.db.Where("id = ?", id).First(&user).Error; err != nil {
+		return models.User{}, err
+	}
+	return user, nil
+}
+
+// GetAll returns all users
+func (r *UserRepository) GetAll() ([]models.User, error) {
+	var users []models.User
+	if err := r.db.Find(&users).Error; err != nil {
+		return []models.User{}, err
+	}
+	return users, nil
+}
+
+// Create creates a new user
+func (r *UserRepository) Create(user models.User) (models.User, error) {
+	if err := r.db.Create(&user).Error; err != nil {
+		return models.User{}, err
+	}
+	return user, nil
+}
+
+// Update updates a user
+func (r *UserRepository) Update(user models.User) error {
+	return r.db.Save(&user).Error
+}
+
+// Delete deletes a user by their ID
+func (r *UserRepository) Delete(id string) error {
+	return r.db.Delete(&models.User{}, id).Error
+}
+
+// HardDelete deletes a user by their ID
+func (r *UserRepository) HardDelete(user models.User) error {
+	return r.db.Unscoped().Delete(&user).Error
+}