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/_template/field_mapping.tmpl

@@ -0,0 +1,48 @@
+{{- /*gotype: go.mau.fi/mautrix-telegram/pkg/gotd/gen.structConfig*/ -}}
+{{ define "field_mapping" }}{{- $s := .Struct -}}
+
+{{- range $f := $s.Fields }}{{ if and (not $f.DoubleSlice) (ne ($f.Type) ("bin.Fields")) }}
+{{ if not $f.Slice }}
+
+{{- $mappings := index ($.Config.Mappings) ($f.Type) -}}
+{{- range $mapping := $mappings }}{{- if (not $mapping.Constructor) }}
+{{- /*gotype: go.mau.fi/mautrix-telegram/pkg/gotd/gen.constructorMapping*/ -}}
+// Get{{ $f.Name }}As{{ $mapping.MapperName }} returns mapped value of {{ $f.Name }} {{ if $f.Conditional }}
+{{- if not ($f.ConditionalBool) }}conditional field and
+// boolean which is true if field was set.
+{{- else }}conditional field.
+{{- end }}
+{{- else }}field.
+{{- end }}
+func ({{ $s.Receiver }} *{{ $s.Name }}) Get{{ $f.Name }}As{{ $mapping.MapperName }}() ({{ template "print_mapper_type" $mapping }}, bool) {
+    {{- if $f.Conditional }}
+    if value, ok := {{ $s.Receiver }}.Get{{ $f.Name }}(); ok {
+        return value.As{{ $mapping.MapperName }}()
+    }
+    return nil, false
+    {{- else }}
+    return {{ $s.Receiver }}.{{ $f.Name }}.As{{ $mapping.MapperName }}()
+    {{- end }}
+}
+{{- end }}{{- end }}
+
+{{- else }}
+
+{{- if $f.Interface }}
+// Map{{ $f.Name }} returns field {{ $f.Name }} wrapped in {{ template "slice_field_name" $f }} helper.
+func ({{ $s.Receiver }} *{{ $s.Name }}) Map{{ $f.Name }}() (value {{ template "slice_field_name" $f }}{{ if $f.Conditional }}, ok bool{{ end }}) {
+    {{- if $f.Conditional }}
+    if !{{ $s.Receiver }}.{{ $f.ConditionalField }}.Has({{ $f.ConditionalIndex }}) {
+        return value, false
+    }
+    return {{ template "slice_field_name" $f }}({{ $s.Receiver }}.{{ $f.Name }}), true
+    {{- else }}
+    return {{ template "slice_field_name" $f }}({{ $s.Receiver }}.{{ $f.Name }})
+    {{- end }}
+}
+{{- end }}
+
+{{- end }}
+{{- end }}{{- end }}
+
+{{ end }}