Get Instagram DM messages

Read the messages of a DM conversation by thread_id (get the thread_id from get_inbox). count=0 fetches every page. Returns thread_id, title, users, count, and messages in chronological order (oldest to newest), each with sent_by_me, sender, type, text, timestamp, and date (ISO). Timestamps are microsecond epochs; text is null for non-text items (use type, e.g. clip/media_share/like/action_log); sender is null for your own messages (sent_by_me=true).