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/middleware.go

@@ -0,0 +1,44 @@
+package telegram
+
+import (
+	"context"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// InvokeFunc implements tg.Invoker as function.
+type InvokeFunc func(ctx context.Context, input bin.Encoder, output bin.Decoder) error
+
+// Invoke implements tg.Invoker.
+func (i InvokeFunc) Invoke(ctx context.Context, input bin.Encoder, output bin.Decoder) error {
+	return i(ctx, input, output)
+}
+
+// Middleware returns new InvokeFunc for next invoker.
+type Middleware interface {
+	Handle(next tg.Invoker) InvokeFunc
+}
+
+// MiddlewareFunc implements Middleware as function.
+type MiddlewareFunc func(next tg.Invoker) InvokeFunc
+
+// Handle implements Middleware.
+func (m MiddlewareFunc) Handle(next tg.Invoker) InvokeFunc { return m(next) }
+
+// chainMiddlewares composes new invoker in such order that first element in
+// chain is called first, and latest "next" argument will be "invoker".
+//
+// E.g. we have invoker and two middlewares, so order will be following:
+// 0, 1, (invoker), 1 (after "next"), 0 (after "next").
+//
+// See TestMiddlewareOrder or ExampleMiddleware.
+func chainMiddlewares(invoker tg.Invoker, chain ...Middleware) tg.Invoker {
+	if len(chain) == 0 {
+		return invoker
+	}
+	for i := len(chain) - 1; i >= 0; i-- {
+		invoker = chain[i].Handle(invoker)
+	}
+	return invoker
+}