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/constant/tdlib_ids.go

@@ -0,0 +1,64 @@
+package constant
+
+const (
+	// MaxTDLibChatID is maximum chat TDLib ID.
+	MaxTDLibChatID = 999999999999
+	// MaxTDLibChannelID is maximum channel TDLib ID.
+	MaxTDLibChannelID = 1000000000000 - int64(1<<31)
+	// ZeroTDLibChannelID is minimum channel TDLib ID.
+	ZeroTDLibChannelID = -1000000000000
+	// ZeroTDLibSecretChatID is minimum secret chat TDLib ID.
+	ZeroTDLibSecretChatID = -2000000000000
+	// MaxTDLibUserID is maximum user TDLib ID.
+	MaxTDLibUserID = (1 << 40) - 1
+)
+
+// TDLibPeerID is TDLib's peer ID.
+type TDLibPeerID int64
+
+// User sets TDLibPeerID value as user.
+func (id *TDLibPeerID) User(p int64) {
+	*id = TDLibPeerID(p)
+}
+
+// Chat sets TDLibPeerID value as chat.
+func (id *TDLibPeerID) Chat(p int64) {
+	*id = TDLibPeerID(-p)
+}
+
+// Channel sets TDLibPeerID value as channel.
+func (id *TDLibPeerID) Channel(p int64) {
+	*id = TDLibPeerID(ZeroTDLibChannelID + (p * -1))
+}
+
+// ToPlain converts TDLib ID to plain ID.
+func (id TDLibPeerID) ToPlain() (r int64) {
+	switch {
+	case id.IsUser():
+		r = int64(id)
+	case id.IsChat():
+		r = int64(-id)
+	case id.IsChannel():
+		r = int64(id) - ZeroTDLibChannelID
+		r = -r
+	}
+	return r
+}
+
+// IsUser whether that given ID is user ID.
+func (id TDLibPeerID) IsUser() bool {
+	return id > 0 && id <= MaxTDLibUserID
+}
+
+// IsChat whether that given ID is chat ID.
+func (id TDLibPeerID) IsChat() bool {
+	return id < 0 && -MaxTDLibChatID <= id
+}
+
+// IsChannel whether that given ID is channel ID.
+func (id TDLibPeerID) IsChannel() bool {
+	return id < 0 &&
+		id != ZeroTDLibChannelID &&
+		!id.IsChat() &&
+		ZeroTDLibChannelID-TDLibPeerID(MaxTDLibChannelID) <= id
+}