feat(chat): implement GetChat, GetUserProfilePhotos, chat sticker set, admin title

Fill deferred methods: GetChat (peer info), GetUserProfilePhotos
(photos.getUserPhotos with paging), SetChatStickerSet/DeleteChatStickerSet
(channels.setStickers) and SetChatAdministratorCustomTitle (preserves
existing rights via getParticipant + editAdmin). Drop them from the
conformance deferred list.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ernado

chat_admin.go

@@ -138,3 +138,33 @@ func (b *Bot) SetChatPermissions(ctx context.Context, chat ChatID, permissions C
 	}
 	return nil
 }
+
+// SetChatStickerSet sets the group sticker set for a supergroup.
+func (b *Bot) SetChatStickerSet(ctx context.Context, chat ChatID, stickerSetName string) error {
+	channel, err := b.resolveChannel(ctx, chat)
+	if err != nil {
+		return err
+	}
+	if _, err := b.raw.ChannelsSetStickers(ctx, &tg.ChannelsSetStickersRequest{
+		Channel:    channel,
+		Stickerset: &tg.InputStickerSetShortName{ShortName: stickerSetName},
+	}); err != nil {
+		return asAPIError(err)
+	}
+	return nil
+}
+
+// DeleteChatStickerSet removes the group sticker set from a supergroup.
+func (b *Bot) DeleteChatStickerSet(ctx context.Context, chat ChatID) error {
+	channel, err := b.resolveChannel(ctx, chat)
+	if err != nil {
+		return err
+	}
+	if _, err := b.raw.ChannelsSetStickers(ctx, &tg.ChannelsSetStickersRequest{
+		Channel:    channel,
+		Stickerset: &tg.InputStickerSetEmpty{},
+	}); err != nil {
+		return asAPIError(err)
+	}
+	return nil
+}

chat_info.go

@@ -0,0 +1,78 @@
+package botapi
+
+import (
+	"context"
+
+	"github.com/gotd/td/tg"
+)
+
+// GetChat returns up-to-date information about a chat.
+func (b *Bot) GetChat(ctx context.Context, chat ChatID) (*Chat, error) {
+	p, err := b.resolvePeer(ctx, chat)
+	if err != nil {
+		return nil, err
+	}
+	c := chatFromPeer(p)
+	return &c, nil
+}
+
+// GetUserProfilePhotosOption configures a GetUserProfilePhotos call.
+type GetUserProfilePhotosOption func(*userPhotosConfig)
+
+type userPhotosConfig struct {
+	offset int
+	limit  int
+}
+
+// WithProfilePhotosOffset sets the number of photos to skip.
+func WithProfilePhotosOffset(offset int) GetUserProfilePhotosOption {
+	return func(c *userPhotosConfig) { c.offset = offset }
+}
+
+// WithProfilePhotosLimit caps the number of photos returned (1-100).
+func WithProfilePhotosLimit(limit int) GetUserProfilePhotosOption {
+	return func(c *userPhotosConfig) { c.limit = limit }
+}
+
+// GetUserProfilePhotos returns a user's profile photos.
+func (b *Bot) GetUserProfilePhotos(ctx context.Context, userID int64, opts ...GetUserProfilePhotosOption) (*UserProfilePhotos, error) {
+	cfg := userPhotosConfig{limit: 100}
+	for _, o := range opts {
+		o(&cfg)
+	}
+
+	user, err := b.resolveInputUser(ctx, userID)
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := b.raw.PhotosGetUserPhotos(ctx, &tg.PhotosGetUserPhotosRequest{
+		UserID: user,
+		Offset: cfg.offset,
+		Limit:  cfg.limit,
+	})
+	if err != nil {
+		return nil, asAPIError(err)
+	}
+
+	var (
+		photos []tg.PhotoClass
+		total  int
+	)
+	switch p := res.(type) {
+	case *tg.PhotosPhotos:
+		photos = p.Photos
+		total = len(p.Photos)
+	case *tg.PhotosPhotosSlice:
+		photos = p.Photos
+		total = p.Count
+	}
+
+	out := &UserProfilePhotos{TotalCount: total}
+	for _, ph := range photos {
+		if photo, ok := ph.(*tg.Photo); ok {
+			out.Photos = append(out.Photos, photoSizesFromTg(photo))
+		}
+	}
+	return out, nil
+}

chat_member_methods.go

@@ -239,3 +239,39 @@ func userToInputPeer(u tg.InputUserClass) tg.InputPeerClass {
 		return &tg.InputPeerEmpty{}
 	}
 }
+
+// SetChatAdministratorCustomTitle sets a custom title (rank) for an
+// administrator that the bot has promoted in a supergroup. It preserves the
+// administrator's existing rights.
+func (b *Bot) SetChatAdministratorCustomTitle(ctx context.Context, chat ChatID, userID int64, customTitle string) error {
+	channel, err := b.resolveChannel(ctx, chat)
+	if err != nil {
+		return err
+	}
+	user, err := b.resolveInputUser(ctx, userID)
+	if err != nil {
+		return err
+	}
+
+	res, err := b.raw.ChannelsGetParticipant(ctx, &tg.ChannelsGetParticipantRequest{
+		Channel:     channel,
+		Participant: userToInputPeer(user),
+	})
+	if err != nil {
+		return asAPIError(err)
+	}
+	admin, ok := res.Participant.(*tg.ChannelParticipantAdmin)
+	if !ok {
+		return &Error{Code: 400, Description: "Bad Request: user is not an administrator"}
+	}
+
+	if _, err := b.raw.ChannelsEditAdmin(ctx, &tg.ChannelsEditAdminRequest{
+		Channel:     channel,
+		UserID:      user,
+		AdminRights: admin.AdminRights,
+		Rank:        customTitle,
+	}); err != nil {
+		return asAPIError(err)
+	}
+	return nil
+}

conformance_test.go

@@ -21,22 +21,17 @@ var coveredByOtherMeans = map[string]string{
 // implemented. Each is an acknowledged gap tracked in docs/roadmap.md; the
 // conformance test allows them so it can still catch *unacknowledged* drift.
 var deferredMethods = map[string]string{
-	"editMessageMedia":                "Phase 3 deferred",
-	"answerPreCheckoutQuery":          "payments — deferred until payment updates land",
-	"answerShippingQuery":             "payments — deferred until payment updates land",
-	"sendInvoice":                     "payments — deferred",
-	"setPassportDataErrors":           "Telegram Passport — deferred",
-	"sendGame":                        "games — deferred",
-	"setGameScore":                    "games — deferred",
-	"getGameHighScores":               "games — deferred",
-	"getStickerSet":                   "stickers — deferred (needs Sticker[] conversion)",
-	"setStickerSetThumb":              "stickers — deferred",
-	"getChat":                         "chat info — deferred",
-	"getUserProfilePhotos":            "deferred",
-	"setChatStickerSet":               "chat sticker set — deferred",
-	"deleteChatStickerSet":            "chat sticker set — deferred",
-	"setChatAdministratorCustomTitle": "member management — deferred",
-	"stopPoll":                        "deferred",
+	"editMessageMedia":       "Phase 3 deferred",
+	"answerPreCheckoutQuery": "payments — deferred until payment updates land",
+	"answerShippingQuery":    "payments — deferred until payment updates land",
+	"sendInvoice":            "payments — deferred",
+	"setPassportDataErrors":  "Telegram Passport — deferred",
+	"sendGame":               "games — deferred",
+	"setGameScore":           "games — deferred",
+	"getGameHighScores":      "games — deferred",
+	"getStickerSet":          "stickers — deferred (needs Sticker[] conversion)",
+	"setStickerSetThumb":     "stickers — deferred",
+	"stopPoll":               "deferred",
 }
 
 // notApplicableMethods lists published methods that do not apply to the