feat: Add BE changes for captain pdf support for faq generation (#12113)

enterprise/app/views/api/v1/models/captain/_document.json.jbuilder

@@ -3,8 +3,11 @@ json.assistant do
   json.partial! 'api/v1/models/captain/assistant', formats: [:json], resource: resource.assistant
 end
 json.content resource.content
+json.content_type resource.content_type
 json.created_at resource.created_at.to_i
 json.external_link resource.external_link
+json.display_url resource.display_url
+json.file_size resource.file_size
 json.id resource.id
 json.name resource.name
 json.status resource.status