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/auth/status.go

@@ -0,0 +1,60 @@
+package auth
+
+import (
+	"context"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// Status represents authorization status.
+type Status struct {
+	// Authorized is true if client is authorized.
+	Authorized bool
+	// User is current User object.
+	User *tg.User
+}
+
+// Status gets authorization status of client.
+func (c *Client) Status(ctx context.Context) (*Status, error) {
+	u, err := c.self(ctx)
+	if IsUnauthorized(err) {
+		return &Status{}, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	return &Status{
+		Authorized: true,
+		User:       u,
+	}, nil
+}
+
+// IfNecessary runs given auth flow if current session is not authorized.
+func (c *Client) IfNecessary(ctx context.Context, flow Flow) error {
+	auth, err := c.Status(ctx)
+	if err != nil {
+		return errors.Wrap(err, "get auth status")
+	}
+	if auth.Authorized {
+		return nil
+	}
+	if err := flow.Run(ctx, c); err != nil {
+		return errors.Wrap(err, "auth flow")
+	}
+	return nil
+}
+
+// Test creates and runs auth flow using Test authenticator
+// if current session is not authorized.
+func (c *Client) Test(ctx context.Context, dc int) error {
+	return c.IfNecessary(ctx, NewFlow(Test(c.rand, dc), SendCodeOptions{}))
+}
+
+// TestUser creates and runs auth flow using TestUser authenticator
+// if current session is not authorized.
+func (c *Client) TestUser(ctx context.Context, phone string, dc int) error {
+	return c.IfNecessary(ctx, NewFlow(TestUser(phone, dc), SendCodeOptions{}))
+}