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/tgtest/conns.go

@@ -0,0 +1,92 @@
+package tgtest
+
+import (
+	"sync"
+
+	"go.uber.org/atomic"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/crypto"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/transport"
+)
+
+type connection struct {
+	transport.Conn
+	sent atomic.Bool
+}
+
+func (conn *connection) sentCreated() bool {
+	return conn.sent.Swap(true)
+}
+
+// users contains all server connections and sessions.
+type users struct {
+	sessions    map[[8]byte]crypto.AuthKey
+	sessionsMux sync.Mutex
+
+	conns    map[int64]*connection
+	connsMux sync.Mutex
+}
+
+func newUsers() *users {
+	return &users{
+		conns:    map[int64]*connection{},
+		sessions: map[[8]byte]crypto.AuthKey{},
+	}
+}
+
+func (c *users) createConnection(key int64, tConn transport.Conn) *connection {
+	c.connsMux.Lock()
+	defer c.connsMux.Unlock()
+
+	if v, ok := c.conns[key]; ok {
+		return v
+	}
+
+	conn := &connection{
+		Conn: tConn,
+	}
+	c.conns[key] = conn
+	return conn
+}
+
+func (c *users) getConnection(key int64) (conn *connection, ok bool) {
+	c.connsMux.Lock()
+	conn, ok = c.conns[key]
+	c.connsMux.Unlock()
+
+	return
+}
+
+func (c *users) deleteConnection(key int64) {
+	c.connsMux.Lock()
+	conn := c.conns[key]
+	if conn != nil {
+		_ = conn.Close()
+	}
+	delete(c.conns, key)
+	c.connsMux.Unlock()
+}
+
+func (c *users) addSession(key crypto.AuthKey) {
+	c.sessionsMux.Lock()
+	c.sessions[key.ID] = key
+	c.sessionsMux.Unlock()
+}
+
+func (c *users) getSession(k [8]byte) (s crypto.AuthKey, ok bool) {
+	c.connsMux.Lock()
+	s, ok = c.sessions[k]
+	c.connsMux.Unlock()
+
+	return
+}
+
+func (c *users) Close() error {
+	c.connsMux.Lock()
+	for _, conn := range c.conns {
+		_ = conn.Close()
+	}
+	c.connsMux.Unlock()
+
+	return nil
+}