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>

spec/builders/messages/facebook/message_builder_spec.rb

@@ -140,6 +140,66 @@ describe Messages::Facebook::MessageBuilder do
       end
     end
 
+    context 'when message contains a sticker attachment' do
+      let(:sticker_url) { 'https://scontent.xx.fbcdn.net/sticker.png' }
+      let(:sticker_message_object) do
+        {
+          messaging: {
+            sender: { id: '3383290475046708' },
+            recipient: { id: facebook_channel.page_id },
+            timestamp: 1_772_452_164_516,
+            message: {
+              mid: 'm_sticker_test',
+              attachments: [
+                { type: 'image', payload: { url: sticker_url } },
+                { type: 'sticker', payload: { url: sticker_url } }
+              ]
+            }
+          }
+        }.to_json
+      end
+      let(:sticker_message) { Integrations::Facebook::MessageParser.new(sticker_message_object) }
+
+      before do
+        allow(Koala::Facebook::API).to receive(:new).and_return(fb_object)
+        allow(fb_object).to receive(:get_object).and_return(
+          { first_name: 'Jane', last_name: 'Dae', profile_pic: 'https://chatwoot-assets.local/sample.png' }.with_indifferent_access
+        )
+        stub_request(:get, sticker_url).to_return(status: 200, body: 'sticker_data', headers: { 'Content-Type' => 'image/png' })
+      end
+
+      it 'stores the sticker as a single image attachment' do
+        described_class.new(sticker_message, facebook_channel.inbox).perform
+
+        message = facebook_channel.inbox.messages.find_by(source_id: 'm_sticker_test')
+        expect(message.attachments.count).to eq(1)
+        expect(message.attachments.first.file_type).to eq('image')
+        expect(message.attachments.first.external_url).to eq(sticker_url)
+      end
+
+      it 'keeps duplicate non-sticker attachments that share a URL' do
+        duplicate_image_object = {
+          messaging: {
+            sender: { id: '3383290475046708' },
+            recipient: { id: facebook_channel.page_id },
+            message: {
+              mid: 'm_duplicate_image_test',
+              attachments: [
+                { type: 'image', payload: { url: sticker_url } },
+                { type: 'image', payload: { url: sticker_url } }
+              ]
+            }
+          }
+        }.to_json
+        duplicate_image_message = Integrations::Facebook::MessageParser.new(duplicate_image_object)
+
+        described_class.new(duplicate_image_message, facebook_channel.inbox).perform
+
+        message = facebook_channel.inbox.messages.find_by(source_id: 'm_duplicate_image_test')
+        expect(message.attachments.count).to eq(2)
+      end
+    end
+
     [
       {
         source_id: 'm_fallback_test',