When using paging with rest, the X-Total-Count header and the in json @total_size
properties match the returned content. It should match all the items returned
before pagination.

That info isn't directly available at the rest.py level. The pagination is pushed
down into the database via the filter method. In the rdbms db at least we use OFFSET
and LIMIT in the db query, so the full list of matching items isn't available.

Maybe change docs to remove X-Total-Count header? Returned @total_size to @returned_size
or something similar. Might be able to estimate this number but performing a count()
at the db level might be possible but is the run time worth it?