fix: Paginate attachments API (#11044)

There are attachments with over 1000 attachments (unusual) in
production, and some of them timeout. This PR would limit the number of
attachments to 100 (which is sufficient for viewing the files in the
gallery, pagination on the UI can be added later).

app/controllers/api/v1/accounts/conversations_controller.rb

@@ -6,6 +6,8 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
   before_action :conversation, except: [:index, :meta, :search, :create, :filter]
   before_action :inbox, :contact, :contact_inbox, only: [:create]
 
+  ATTACHMENT_RESULTS_PER_PAGE = 100
+
   def index
     result = conversation_finder.perform
     @conversations = result[:conversations]
@@ -24,7 +26,12 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
   end
 
   def attachments
+    @attachments_count = @conversation.attachments.count
     @attachments = @conversation.attachments
+                                .includes(:message)
+                                .order(created_at: :desc)
+                                .page(attachment_params[:page])
+                                .per(ATTACHMENT_RESULTS_PER_PAGE)
   end
 
   def show; end
@@ -124,6 +131,10 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
     params.permit(:priority)
   end
 
+  def attachment_params
+    params.permit(:page)
+  end
+
   def update_last_seen_on_conversation(last_seen_at, update_assignee)
     # rubocop:disable Rails/SkipsModelValidations
     @conversation.update_column(:agent_last_seen_at, last_seen_at)

app/views/api/v1/accounts/conversations/attachments.json.jbuilder

@@ -1,3 +1,7 @@
+json.meta do
+  json.total_count @attachments_count
+end
+
 json.payload @attachments do |attachment|
   json.message_id attachment.push_event_data[:message_id]
   json.thumb_url attachment.push_event_data[:thumb_url]