test(telegram): fix business-chat send-attachments spec

The let(:channel) and the service's message.inbox.channel were different
object instances, so the chat_id / business_connection_id stubs on the
test instance never applied to the service. Other examples masked it
because they only counted requests; the business-chat example matches
on body and tripped. Set the values via conversation.additional_attributes
(where the channel methods actually read from) instead of stubbing.

spec/services/telegram/send_attachments_service_spec.rb

@@ -3,13 +3,17 @@ require 'rails_helper'
 RSpec.describe Telegram::SendAttachmentsService do
   describe '#perform' do
     let(:channel) { create(:channel_telegram) }
-    let(:message) { build(:message, conversation: create(:conversation, inbox: channel.inbox)) }
+    # Channel#chat_id and #business_connection_id read from conversation.additional_attributes,
+    # so set the values there directly — stubbing the let(:channel) instance doesn't affect
+    # the service's message.inbox.channel reference (different object instance).
+    let(:conversation) do
+      create(:conversation, inbox: channel.inbox, additional_attributes: { 'chat_id' => 'chat123' })
+    end
+    let(:message) { build(:message, conversation: conversation) }
     let(:service) { described_class.new(message: message) }
     let(:telegram_api_url) { channel.telegram_api_url }
 
     before do
-      allow(channel).to receive(:chat_id).and_return('chat123')
-
       stub_request(:post, "#{telegram_api_url}/sendMediaGroup")
         .to_return(status: 200, body: { ok: true, result: [{ message_id: 'media' }] }.to_json, headers: { 'Content-Type' => 'application/json' })
 
@@ -41,7 +45,11 @@ RSpec.describe Telegram::SendAttachmentsService do
     end
 
     context 'when this is business chat' do
-      before { allow(channel).to receive(:business_connection_id).and_return('eooW3KF5WB5HxTD7T826') }
+      before do
+        conversation.update!(additional_attributes: conversation.additional_attributes.merge(
+          'business_connection_id' => 'eooW3KF5WB5HxTD7T826'
+        ))
+      end
 
       it 'sends all types of attachments in seperate groups and returns the last successful message ID from the batch' do
         attach_files(message)