Surface in:all as an option in the Advanced Search UI

I’ve got a couple of sites which make extensive use of Group Messages, which is a great way to have ‘off Forum’ topics clearly delineated from the open Categories.

However, this gives a bit of a functional search silo. While it is possible to search across Messages and the wider forum using in-all (see Searching for content effectively), it isn’t actually possible to access this from the search UI.

For our use case, it would be very helpful to have in the Advance Search UI:

  1. An easy-to-use option to control if Messages (and/or Chat) are included in search

    • this could work as an additional drop-down option nicely here:
    • or maybe easier as one of the checkboxes here (as these simply instert the prefex into the search bar):
  2. The ability to set a site-wide default for this