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/dispatcher.go

@@ -0,0 +1,82 @@
+package tgtest
+
+import (
+	"sync"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+)
+
+// Dispatcher is a plain handler to map requests by ID.
+type Dispatcher struct {
+	reqs     map[uint32]Handler
+	mux      sync.Mutex
+	fallback Handler
+}
+
+// NewDispatcher creates new Dispatcher.
+func NewDispatcher() *Dispatcher {
+	return &Dispatcher{
+		reqs: map[uint32]Handler{},
+	}
+}
+
+// OnMessage implements Handler
+func (d *Dispatcher) OnMessage(server *Server, req *Request) error {
+	id, err := req.Buf.PeekID()
+	if err != nil {
+		return errors.Wrap(err, "peek id")
+	}
+
+	d.mux.Lock()
+	h, ok := d.reqs[id]
+	fallback := d.fallback
+	d.mux.Unlock()
+	if ok {
+		return h.OnMessage(server, req)
+	}
+
+	if fallback != nil {
+		return fallback.OnMessage(server, req)
+	}
+
+	return errors.Errorf("unexpected type %#x", id)
+}
+
+// Handle sets handler for given TypeID.
+func (d *Dispatcher) Handle(id uint32, h Handler) *Dispatcher {
+	d.mux.Lock()
+	d.reqs[id] = h
+	d.mux.Unlock()
+	return d
+}
+
+// HandleFunc sets handler for given TypeID.
+func (d *Dispatcher) HandleFunc(id uint32, h func(server *Server, req *Request) error) *Dispatcher {
+	return d.Handle(id, HandlerFunc(h))
+}
+
+// Result sets constant result for given TypeID.
+// NB: it uses rpc_result to pack given encoder.
+func (d *Dispatcher) Result(id uint32, msg bin.Encoder) *Dispatcher {
+	return d.HandleFunc(id, func(server *Server, req *Request) error {
+		return server.SendResult(req, msg)
+	})
+}
+
+// Vector sets constant Vector result for given TypeID.
+// NB: it uses rpc_result to pack generic vector with given encoders.
+func (d *Dispatcher) Vector(id uint32, msgs ...bin.Encoder) *Dispatcher {
+	return d.HandleFunc(id, func(server *Server, req *Request) error {
+		return server.SendVector(req, msgs...)
+	})
+}
+
+// Fallback sets fallback handler.
+func (d *Dispatcher) Fallback(h Handler) *Dispatcher {
+	d.mux.Lock()
+	d.fallback = h
+	d.mux.Unlock()
+	return d
+}