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/message/entity/format_test.go

@@ -0,0 +1,71 @@
+package entity
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+func TestBuilder_TextRange(t *testing.T) {
+	var (
+		a = require.New(t)
+		b Builder
+	)
+	_, _ = b.WriteString("abc")
+	a.Equal("abc"[1:2], b.TextRange(1, 2))
+	a.Equal("abc"[0:0], b.TextRange(0, 0))
+
+	panicRanges := [][2]int{
+		{1, 0},
+		{-1, 0},
+		{0, -1},
+	}
+	for _, r := range panicRanges {
+		a.Panics(func() {
+			b.TextRange(r[0], r[1])
+		})
+	}
+}
+
+func TestBuilder_LastEntity(t *testing.T) {
+	var (
+		a = require.New(t)
+		b Builder
+	)
+
+	e, ok := b.LastEntity()
+	a.False(ok)
+	a.Nil(e)
+	b.Underline("abc")
+	e, ok = b.LastEntity()
+	a.True(ok)
+	a.Equal(&tg.MessageEntityUnderline{
+		Offset: 0,
+		Length: 3,
+	}, e)
+}
+
+func TestBuilder_GrowText(t *testing.T) {
+	var (
+		a = require.New(t)
+		b Builder
+	)
+
+	b.GrowText(100)
+	a.LessOrEqual(100, b.message.Cap())
+}
+
+func TestBuilder_GrowEntities(t *testing.T) {
+	var (
+		a = require.New(t)
+		b Builder
+	)
+
+	b.GrowEntities(100)
+	a.Equal(100, cap(b.entities))
+	a.Panics(func() {
+		b.GrowEntities(-1)
+	})
+}