cubicweb #3406930 formfields.CompoundField does not handle multipart properly [validation pending]

If there's a FileField within a CompoundField, the latter will not have the enctype multipart set, despite the FileField needs it.

CompoundField should inspect its children fields to determine whether it needs multipart.

prioritynormal
typebug
done in3.19.0
load1.000
load left0.000
closed by#6012cf57f48e [web/formfields] Make CompoundField inherit needs_multipart from its subfields
patch[web/formfields] Make CompoundField inherit needs_multipart from its subfields [applied]