fix(facebook): handle messenger sticker attachment type (#14793)

Facebook Messenger sticker messages no longer break message ingestion.
Meta recently changed its webhook payloads so a sticker now arrives as a
new `sticker` attachment type (alongside the existing `image` attachment
during the transition period). Chatwoot didn't recognise `sticker` as a
valid attachment file type, so the webhook job crashed and the message —
and any others in the same batch — failed to sync. Stickers now appear
in the conversation as a single image, just like before.

Fixes https://linear.app/chatwoot/issue/PLA-177

## How to reproduce

1. Connect a Facebook Page inbox.
2. Send a sticker from Messenger to that page.
3. Before this change: the `Webhooks::FacebookEventsJob` raises
`ArgumentError: 'sticker' is not a valid file_type` and the message is
dropped.
4. After this change: the sticker shows up in the conversation as a
single image attachment.

---------

Co-authored-by: Muhsin <12408980+muhsin-k@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/builders/messages/messenger/message_builder.rb

@@ -6,6 +6,11 @@ class Messages::Messenger::MessageBuilder
     return if unsupported_file_type?(attachment['type'])
 
     params = attachment_params(attachment)
+    # During Meta's sticker webhook transition, a sticker message carries both an `image`
+    # and a `sticker` attachment pointing to the same URL. Skip the redundant sticker so it
+    # isn't attached twice, while still storing legitimate duplicate attachments of other types.
+    return if duplicate_sticker?(attachment, params[:external_url])
+
     attachment_obj = @message.attachments.new(params.except(:remote_file_url))
     attachment_obj.save!
     if facebook_reel?(attachment)
@@ -13,10 +18,14 @@ class Messages::Messenger::MessageBuilder
     elsif params[:remote_file_url]
       attach_file(attachment_obj, params[:remote_file_url])
     end
+    fetch_attachment_links(attachment_obj)
+    update_attachment_file_type(attachment_obj)
+  end
+
+  def fetch_attachment_links(attachment_obj)
     fetch_story_link(attachment_obj) if attachment_obj.file_type == 'story_mention'
     fetch_ig_story_link(attachment_obj) if attachment_obj.file_type == 'ig_story'
     fetch_ig_post_link(attachment_obj) if attachment_obj.file_type == 'ig_post'
-    update_attachment_file_type(attachment_obj)
   end
 
   def attach_file(attachment, file_url)
@@ -111,13 +120,20 @@ class Messages::Messenger::MessageBuilder
 
   # Facebook may send attachment types that don't directly match our file_type enum.
   # Map known aliases to their canonical enum values.
-  FACEBOOK_FILE_TYPE_MAP = { reel: :ig_reel }.freeze
+  FACEBOOK_FILE_TYPE_MAP = { reel: :ig_reel, sticker: :image }.freeze
 
   def normalize_file_type(type)
     sym = type.to_sym
     FACEBOOK_FILE_TYPE_MAP.fetch(sym, sym)
   end
 
+  def duplicate_sticker?(attachment, url)
+    return false unless attachment['type'].to_sym == :sticker
+    return false if url.blank?
+
+    @message.attachments.any? { |existing| existing.external_url == url }
+  end
+
   # Facebook sends reel URLs as webpage links (facebook.com/reel/...) rather than
   # direct video URLs. Downloading these yields HTML, not video content.
   def facebook_reel?(attachment)