Use Noto Sans to gracefully handle inserting custom text
on PDF's. Previously we were using Helvetica which is a
standard PDF font but that would fail for any character
that couldn't be encoded in WinANSI.
Noto Sans was chosen as it has support for a large number
of languages and glyphs with challenges now being adding
support for CJK glyphs.
Previously we used the form flattening method from PDF-Lib
but unfortunately when it encountered orphaned form items
or other PDF oddities it would throw an error.
Because of this certain documents would fail to seal and
be stuck in a pending state with no recourse available.
This change rewrites the form flattening handler to be
more lenient when coming across the unknown opting to skip
items it can't handle rather than abort.
