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/gen/templates.go

@@ -0,0 +1,110 @@
+package gen
+
+import (
+	"embed"
+	"strings"
+	"text/template"
+)
+
+var goKeywords = map[string]struct{}{
+	// See https://golang.org/ref/spec#Keywords.
+	"break":       {},
+	"default":     {},
+	"func":        {},
+	"interface":   {},
+	"select":      {},
+	"case":        {},
+	"defer":       {},
+	"go":          {},
+	"map":         {},
+	"struct":      {},
+	"chan":        {},
+	"else":        {},
+	"goto":        {},
+	"package":     {},
+	"switch":      {},
+	"const":       {},
+	"fallthrough": {},
+	"if":          {},
+	"range":       {},
+	"type":        {},
+	"continue":    {},
+	"for":         {},
+	"import":      {},
+	"return":      {},
+	"var":         {},
+
+	// Not really keyword, but unlikely to shadow.
+	// See go/types/universe.go.
+	"append":  {},
+	"cap":     {},
+	"close":   {},
+	"complex": {},
+	"copy":    {},
+	"delete":  {},
+	"imag":    {},
+	"len":     {},
+	"make":    {},
+	"new":     {},
+	"panic":   {},
+	"print":   {},
+	"println": {},
+	"real":    {},
+	"recover": {},
+}
+
+// Funcs returns functions which used in templates.
+func Funcs() template.FuncMap {
+	return template.FuncMap{
+		"trim":                 strings.TrimSpace,
+		"lower":                strings.ToLower,
+		"trimPrefix":           strings.TrimPrefix,
+		"trimSuffix":           strings.TrimSuffix,
+		"hasPrefix":            strings.HasPrefix,
+		"hasSuffix":            strings.HasSuffix,
+		"contains":             strings.Contains,
+		"hasField":             hasField,
+		"optionalField":        optionalField,
+		"mapCollectableFields": mapCollectableFields,
+		"sortableFields":       sortableFields,
+		"generateSliceHelper":  generateSliceHelper,
+		"concat": func(args ...interface{}) []interface{} {
+			return args
+		},
+		"add": func(x, y int) int {
+			return x + y
+		},
+		"notEmpty": func(s string) bool {
+			return strings.TrimSpace(s) != ""
+		},
+		"lowerGo": func(input string) string {
+			lower := strings.ToLower(input)
+			if _, ok := goKeywords[lower]; ok {
+				return lower + "_"
+			}
+			return lower
+		},
+		"hasFlags": func(def structDef) bool {
+			for _, field := range def.Fields {
+				if field.Type == flagsType {
+					return true
+				}
+			}
+			return false
+		},
+
+		// Argument constructors
+		"newStructConfig":    newStructConfig,
+		"newInterfaceConfig": newInterfaceConfig,
+	}
+}
+
+//go:embed _template/*.tmpl
+var templates embed.FS
+
+// Template parses and returns vendored code generation templates.
+func Template() *template.Template {
+	tmpl := template.New("templates").Funcs(Funcs())
+	tmpl = template.Must(tmpl.ParseFS(templates, "_template/*.tmpl"))
+	return tmpl
+}