feat: Implement storage provider management functionality

- Added new routes and handlers for managing storage providers, including creation, editing, and deletion.
- Introduced a new StorageProvider form component for user input.
- Enhanced the database schema to support storage provider references in transfer configurations.
- Implemented encryption for sensitive fields in storage provider data.
- Added tests for storage provider API endpoints and integration with the database.
- Updated frontend components to support storage provider selection and testing.

internal/encryption/constants.go

@@ -0,0 +1,23 @@
+package encryption
+
+// Key size constants
+const (
+	// AES256KeySize is the key size in bytes for AES-256 encryption (32 bytes = 256 bits)
+	AES256KeySize = 32
+
+	// AESBlockSize is the block size for AES encryption
+	AESBlockSize = 16
+
+	// DefaultKeyEnvVar is the default environment variable name for the encryption key
+	DefaultKeyEnvVar = "GOMFT_ENCRYPTION_KEY"
+
+	// MinKeyLength is the minimum allowed length for encryption keys in bytes
+	MinKeyLength = AES256KeySize
+)
+
+// Error messages
+const (
+	ErrKeyTooShort    = "encryption key is too short, must be at least %d bytes"
+	ErrKeyNotProvided = "encryption key not provided in environment variable %s"
+	ErrInvalidKey     = "provided encryption key is invalid: %s"
+)