feat: add data access layer (repositories)

- Add user repository with CRUD operations and authentication methods
- Add session repository for session management and validation
- Add API key repository for API key management
- Include proper error handling and database transaction support
- Implement search and filtering capabilities

repositories/api-key.go

@@ -0,0 +1,32 @@
+package repositories
+
+import (
+	"git.secnex.io/secnex/idp-api/models"
+	"gorm.io/gorm"
+)
+
+type ApiKeyRepository struct {
+	db *gorm.DB
+}
+
+func NewApiKeyRepository(db *gorm.DB) *ApiKeyRepository {
+	return &ApiKeyRepository{db: db}
+}
+
+func (r *ApiKeyRepository) GetApiKeyByID(id string) (*models.ApiKey, error) {
+	var apiKey models.ApiKey
+	err := r.db.First(&apiKey, "id = ?", id).Error
+	if err != nil {
+		return nil, err
+	}
+	return &apiKey, nil
+}
+
+func (r *ApiKeyRepository) CreateApiKey(apiKey *models.ApiKey) (*models.ApiKey, error) {
+	// Create and return the api key and return the database object
+	result := r.db.Create(apiKey)
+	if result.Error != nil {
+		return nil, result.Error
+	}
+	return apiKey, nil
+}