liftMLValues validated only object-shaped submissions, so a scalar
submitted for a translatable plugin field reached Decode as nil, a
float64 or a bool although pact promises a string; a type that asserts
a string panicked into an opaque 500. decodePluginFields now passes a
string through, turns null into the empty string and refuses any other
value with a 422 on the field before Decode runs.
Jakub Zych
f388d27604