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/index.go

@@ -0,0 +1,10 @@
+package repositories
+
+type Repository interface {
+	GetByID(id string) (interface{}, error) // Get a single entity by ID
+	GetAll() ([]interface{}, error)         // Get all entities
+	Create(entity interface{}) error        // Create a new entity
+	Update(entity interface{}) error        // Update an entity
+	Delete(id string) error                 // Delete an entity by ID
+	HardDelete(entity interface{}) error    // Hard delete an entity
+}