refactor dashboard banner to handle bulk site, team, server

currently we have to create a dashboard banner for every document of those type

either have a child table in the scope section or (much better) some form of doc eval thing - this will very likely run in `get_doc` method in the controllers

Start by examining the controllers' get_doc method and the dashboard banner scope section. Compare how banners are currently created for site, team, and server documents, then determine how bulk handling should be represented. Done means a single dashboard banner can cover the relevant document types without creating one for every document.

Written by the indexing model from the issue text.