Add AES GCM encryption provider

services/secrets/encryption.go

@@ -0,0 +1,16 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package secrets
+
+// EncryptionProvider encrypts and decrypts secrets
+type EncryptionProvider interface {
+	Encrypt(secret, key []byte) ([]byte, error)
+
+	EncryptString(secret string, key []byte) (string, error)
+
+	Decrypt(enc, key []byte) ([]byte, error)
+
+	DecryptString(enc string, key []byte) (string, error)
+}