model/x: serde_fields for transform_offset_options

Signed-off-by: Oren Leiman <oren.leiman@redpanda.com>

src/v/model/transform.h

@@ -160,6 +160,7 @@ struct transform_offset_options
       : serde::
           envelope<latest_offset, serde::version<0>, serde::compat_version<0>> {
         bool operator==(const latest_offset&) const = default;
+        auto serde_fields() { return std::tie(); }
     };
     // A transform can either start at the latest offset, at a timestamp, or at
     // some delta from the start or end of an input partition.