Other: Use msgpack instead of json in vault

msgpack is much faster at serializing and deserializing than json. Using
it in the vault gives a performance boost.

internal/vault/vault_bench_test.go

@@ -0,0 +1,58 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package vault_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/ProtonMail/proton-bridge/v2/internal/vault"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+)
+
+func BenchmarkVault(b *testing.B) {
+	vaultDir, gluonDir := b.TempDir(), b.TempDir()
+
+	// Create a new vault.
+	s, corrupt, err := vault.New(vaultDir, gluonDir, []byte("my secret key"))
+	require.NoError(b, err)
+	require.False(b, corrupt)
+
+	// Add 10kB of cookies to the vault.
+	require.NoError(b, s.SetCookies(bytes.Repeat([]byte("a"), 10_000)))
+
+	// Create 10 vault users.
+	for idx := 0; idx < 10; idx++ {
+		user, err := s.AddUser(uuid.NewString(), "username", "authUID", "authRef", []byte("keyPass"))
+		require.NoError(b, err)
+
+		require.NoError(b, user.SetKeyPass([]byte("new key pass")))
+	}
+
+	b.ResetTimer()
+
+	// Time how quickly we can iterate through the users and get their key pass and bridge pass.
+	for i := 0; i < b.N; i++ {
+		require.NoError(b, s.ForUser(func(user *vault.User) error {
+			require.NotEmpty(b, user.KeyPass())
+			require.NotEmpty(b, user.BridgePass())
+			return nil
+		}))
+	}
+}