Test does not fail if a field's manually-specified type doesn't match the actual type #276
Description
If a field descriptor is explicitly configured with a JsonFieldType and it doesn't match the actual type that can be determined by examining the payload no failure occurs. Arguably, a user should only specify a type for an optional field that isn't present in the payload, i.e. when REST Docs needs some help, but we should still fail when the field is there and it doesn't match the explicitly configured type.