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/cmd/rsagen/main.go

@@ -0,0 +1,147 @@
+// The rsagen command generates rsa.PublicKey variables from PEM-encoded
+// RSA public keys.
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/rsa"
+	"embed"
+	"flag"
+	"fmt"
+	"go/format"
+	"io"
+	"io/fs"
+	"log"
+	"os"
+	"text/template"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/crypto"
+)
+
+//go:embed _template/*.tmpl
+var embedFS embed.FS
+
+var funcs = template.FuncMap{
+	"fingerprint": func(pubkey *rsa.PublicKey) string {
+		return fmt.Sprintf("%08x", uint64(crypto.RSAFingerprint(pubkey)))
+	},
+	"chunks": func(b []byte, size int) [][]byte {
+		var chunks [][]byte
+		for len(b) > size {
+			chunks = append(chunks, b[:size])
+			b = b[size:]
+		}
+		if len(b) != 0 {
+			chunks = append(chunks, b)
+		}
+		return chunks
+	},
+	"single": func(keys []*rsa.PublicKey) (*rsa.PublicKey, error) {
+		if count := len(keys); count != 1 {
+			return nil, errors.Errorf("expected single key, got %d keys", count)
+		}
+		return keys[0], nil
+	},
+}
+
+func main() {
+	if err := run(); err != nil {
+		os.Exit(1)
+	}
+}
+
+func run() error {
+	log.SetFlags(log.Llongfile)
+	var (
+		inPath       = flag.String("f", "", "input path (defaults to stdin)")
+		outPath      = flag.String("o", "", "output path (defaults to stdout)")
+		tplPath      = flag.String("templates", "", "templates directory (defaults to embed)")
+		tplName      = flag.String("exec", "main.tmpl", "template name")
+		pkgName      = flag.String("pkg", "main", "package name")
+		varName      = flag.String("var", "PK", "variable name")
+		singleMode   = flag.Bool("single", false, "emit single key instead of slice")
+		formatOutput = flag.Bool("format", true, "run gofmt on output")
+		testFunc     = flag.String("test", "", "test function name")
+	)
+	flag.Parse()
+
+	if *testFunc == "" {
+		*testFunc = "TestFingerprint" + *varName
+	}
+
+	var err error
+
+	var in []byte
+	if *inPath != "" {
+		in, err = os.ReadFile(*inPath)
+	} else {
+		in, err = io.ReadAll(os.Stdin)
+	}
+	if err != nil {
+		log.Printf("read input: %v", err)
+		return err
+	}
+
+	keys, err := crypto.ParseRSAPublicKeys(in)
+	if err != nil {
+		log.Printf("parse public keys: %v", err)
+		return err
+	}
+
+	fsys, _ := fs.Sub(embedFS, "_template")
+	if *tplPath != "" {
+		fsys = os.DirFS(*tplPath)
+	}
+
+	tpl, err := template.New("").Funcs(funcs).ParseFS(fsys, "*.tmpl")
+	if err != nil {
+		log.Printf("parse templates: %v", err)
+		return err
+	}
+
+	var inLines [][]byte
+	for sc := bufio.NewScanner(bytes.NewReader(in)); sc.Scan(); {
+		line := sc.Bytes()
+		line = bytes.TrimSpace(line)
+		if len(line) == 0 {
+			continue
+		}
+		inLines = append(inLines, line)
+	}
+
+	buf := bytes.NewBuffer(nil)
+	if err := tpl.ExecuteTemplate(buf, *tplName, map[string]interface{}{
+		"Package":    *pkgName,
+		"Variable":   *varName,
+		"Keys":       keys,
+		"Single":     *singleMode,
+		"InputLines": inLines,
+		"TestFunc":   *testFunc,
+	}); err != nil {
+		log.Printf("execute template: %v", err)
+		return err
+	}
+
+	if *formatOutput {
+		p, err := format.Source(buf.Bytes())
+		if err != nil {
+			log.Printf("format output: %v", err)
+			return err
+		}
+		buf = bytes.NewBuffer(p)
+	}
+
+	if *outPath != "" {
+		err = os.WriteFile(*outPath, buf.Bytes(), 0o600)
+	} else {
+		_, err = buf.WriteTo(os.Stdout)
+	}
+	if err != nil {
+		log.Printf("write output: %v", err)
+		return err
+	}
+	return nil
+}