move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/telegram/peers/manager.go

@@ -0,0 +1,46 @@
+package peers
+
+import (
+	"context"
+	"sync"
+
+	"github.com/go-faster/errors"
+	"go.uber.org/zap"
+	"golang.org/x/sync/singleflight"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// Manager is peer manager.
+//
+// NB: this package is completely experimental and still WIP.
+type Manager struct {
+	api     *tg.Client
+	storage Storage
+	cache   Cache
+
+	// State of current user.
+	me *atomicUser
+
+	// needUpdate stores peers what need to be updated.
+	needUpdate     peerIDSet
+	needUpdateFull peerIDSet
+	needUpdateMux  sync.Mutex // guards needUpdate, needUpdateFull
+
+	logger *zap.Logger
+	sg     singleflight.Group
+}
+
+// Init initializes Manager.
+func (m *Manager) Init(ctx context.Context) error {
+	_, err := m.Self(ctx)
+	if err != nil {
+		return errors.Wrap(err, "get self")
+	}
+	return nil
+}
+
+// API returns used Client.
+func (m *Manager) API() *tg.Client {
+	return m.api
+}