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/services/file/storage.go

@@ -0,0 +1,72 @@
+package file
+
+import (
+	"io"
+	"sync"
+	"sync/atomic"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/syncio"
+)
+
+// File represents Telegram file.
+type File interface {
+	io.ReaderAt
+	io.WriterAt
+	io.Closer
+	PartSize() int
+	SetPartSize(v int)
+	Size() int
+}
+
+// Storage is an abstraction for Telegram file storage.
+type Storage interface {
+	Open(name string) (File, error)
+}
+
+type memFile struct {
+	syncio.BufWriterAt
+	partSize int32
+	_        [4]byte
+}
+
+func (m *memFile) Size() int {
+	return m.Len()
+}
+
+func (m *memFile) Close() error {
+	return nil
+}
+
+func (m *memFile) PartSize() int {
+	return int(atomic.LoadInt32(&m.partSize))
+}
+
+func (m *memFile) SetPartSize(v int) {
+	atomic.StoreInt32(&m.partSize, int32(v))
+}
+
+// InMemory is an inmemory implementation of file storage.
+type InMemory struct {
+	files    map[string]*memFile
+	filesMux sync.Mutex
+}
+
+// NewInMemory creates new InMemory.
+func NewInMemory() *InMemory {
+	return &InMemory{
+		files: map[string]*memFile{},
+	}
+}
+
+// Open implement Storage.
+func (i *InMemory) Open(name string) (File, error) {
+	i.filesMux.Lock()
+	defer i.filesMux.Unlock()
+	file, ok := i.files[name]
+	if !ok {
+		file = &memFile{}
+		i.files[name] = file
+	}
+
+	return file, nil
+}