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/bot.go

@@ -0,0 +1,53 @@
+package telegram
+
+import (
+	"context"
+	"os"
+
+	"github.com/go-faster/errors"
+)
+
+// RunUntilCanceled is client callback which
+// locks until client context is canceled.
+func RunUntilCanceled(ctx context.Context, client *Client) error {
+	<-ctx.Done()
+	return ctx.Err()
+}
+
+// BotFromEnvironment creates bot client using ClientFromEnvironment
+// connects to server and authenticates it.
+//
+// Variables:
+// BOT_TOKEN — token from BotFather.
+func BotFromEnvironment(
+	ctx context.Context,
+	opts Options,
+	setup func(ctx context.Context, client *Client) error,
+	cb func(ctx context.Context, client *Client) error,
+) error {
+	client, err := ClientFromEnvironment(opts)
+	if err != nil {
+		return errors.Wrap(err, "create client")
+	}
+
+	if setup != nil {
+		if err := setup(ctx, client); err != nil {
+			return errors.Wrap(err, "setup")
+		}
+	}
+
+	return client.Run(ctx, func(ctx context.Context) error {
+		status, err := client.Auth().Status(ctx)
+		if err != nil {
+			return errors.Wrap(err, "auth status")
+		}
+
+		if !status.Authorized {
+			if _, err := client.Auth().Bot(ctx, os.Getenv("BOT_TOKEN")); err != nil {
+				return errors.Wrap(err, "login")
+			}
+		}
+
+		return cb(ctx, client)
+	})
+}