feat: Add support for grouped file uploads in Slack (#12454)

Fixes
https://linear.app/chatwoot/issue/CW-5646/add-support-for-grouped-file-uploads-in-slack

Previously, when sending multiple attachments to Slack, we uploaded them
one by one. For example, sending 5 images would result in 5 separate
Slack messages. This created clutter and a poor user experience, since
Slack displayed each file as an individual message.
This PR updates the implementation to group all attachments from a
message and send them as a single Slack message. As a result,
attachments now appear together in one grouped block, providing a much
cleaner and more intuitive experience for users.

**Before:** 
Each file uploaded as a separate Slack message.
<img width="400" height="800" alt="before"
src="https://github.com/user-attachments/assets/c8c7f666-549b-428f-bd19-c94e39ed2513"
/>

**After:** 
All files from a single message grouped and displayed together in one
Slack message (similar to how Slack natively handles grouped uploads).
<img width="400" height="800" alt="after"
src="https://github.com/user-attachments/assets/0b1f22d5-4d37-4b84-905a-15e742317e72"
/>

**Changes**

- Upgraded Slack file upload implementation to use the new multiple
attachments API available in slack-ruby-client `v2.7.0`.
- Updated attachment handling to upload all files from a message in a
single API call.
- Enabled proper attachment grouping in Slack, ensuring related files
are presented together.

lib/integrations/slack/send_on_slack_service.rb

@@ -101,7 +101,7 @@ class Integrations::Slack::SendOnSlackService < Base::SendOnChannelService
 
   def send_message
     post_message if message_content.present?
-    upload_file if message.attachments.any?
+    upload_files if message.attachments.any?
   rescue Slack::Web::Api::Errors::AccountInactive, Slack::Web::Api::Errors::MissingScope, Slack::Web::Api::Errors::InvalidAuth,
          Slack::Web::Api::Errors::ChannelNotFound, Slack::Web::Api::Errors::NotInChannel => e
     Rails.logger.error e
@@ -120,36 +120,35 @@ class Integrations::Slack::SendOnSlackService < Base::SendOnChannelService
     )
   end
 
-  def upload_file
-    message.attachments.each do |attachment|
-      next unless attachment.with_attached_file?
+  def upload_files
+    return unless message.attachments.any?
 
-      begin
-        result = slack_client.files_upload_v2(
-          filename: attachment.file.filename.to_s,
-          content: attachment.file.download,
-          initial_comment: 'Attached File!',
-          thread_ts: conversation.identifier,
-          channel_id: hook.reference_id
-        )
-        Rails.logger.info "slack_upload_result: #{result}"
-      rescue Slack::Web::Api::Errors::SlackError => e
-        Rails.logger.error "Failed to upload file #{attachment.file.filename}: #{e.message}"
-      end
+    files = build_files_array
+    return if files.empty?
+
+    begin
+      result = slack_client.files_upload_v2(
+        files: files,
+        initial_comment: 'Attached File!',
+        thread_ts: conversation.identifier,
+        channel_id: hook.reference_id
+      )
+      Rails.logger.info "slack_upload_result: #{result}"
+    rescue Slack::Web::Api::Errors::SlackError => e
+      Rails.logger.error "Failed to upload files: #{e.message}"
     end
   end
 
-  def file_type
-    File.extname(message.attachments.first.download_url).strip.downcase[1..]
-  end
+  def build_files_array
+    message.attachments.filter_map do |attachment|
+      next unless attachment.with_attached_file?
 
-  def file_information
-    {
-      filename: message.attachments.first.file.filename,
-      filetype: file_type,
-      content: message.attachments.first.file.download,
-      title: message.attachments.first.file.filename
-    }
+      {
+        filename: attachment.file.filename.to_s,
+        content: attachment.file.download,
+        title: attachment.file.filename.to_s
+      }
+    end
   end
 
   def sender_name(sender)