PAdES: signing app name for pades signatures
Created by: ydanneg
By a PDF specification It is able to add a signing application name into Sig dictionary. https://www.pdfa.org/norm-refs/SigBuildDict.pdf
This PR adds simple support for adding signing app name into pades signature. Unfortunately ONLY pdfbox supports methods to add this property out of the box. OpenPdf does not support it (requires additional support on their side).
reported as a new feature request https://ec.europa.eu/cefdigital/tracker/browse/DSS-2692