Rebased #5173 onto 9afa1266. Its later-signature predicate is superseded by
#6364's object-based check, so only the /Perms rule lands: under DocMDP P=1 a
/Perms that differs from the signed catalog's, by content, is a structure
change however it was rewritten.
Co-Authored-By: LetoCoder26 <leto@lvanwesten.eu>