[web/formfields] Make CompoundField inherit needs_multipart from its subfields
If there's a FileField within a CompoundField, the latter will not have
the enctype multipart set, even though the FileField needs it.
CompoundField should inspect its children fields to determine whether it
needs multipart.
Closes #3406930.
[MESSAGES CONTROL]
disable-msg = C0301
[VARIABLES]
# Enable / disable this checker
enable-variables = yes
additional-builtins = _, display_name
[BASIC]
required-attributes=
attr-rgx = (w|[a-z_][a-z0-9_]{2,30})
variable-rgx = (w|[a-z_][a-z0-9_]{2,30})$
argument-rgx = (w|[a-z_][a-z0-9_]{2,30})$
[TYPECHECK]
generated-members=debug,info,notice,warning,error,critical,exception