Lookup API now returns a stable response shape

The Lookup API now always emits every payload key declared on the target's scope, even when a particular value is unavailable. Previously, fields backed by data we couldn't produce — most commonly an fdy_outcome_<UNDERSCORED_OUTCOME_ID>_propensity_* field for a person whose Identity Graph data was too sparse for the propensity model to score — were simply absent from the response. Now those fields are always present, with the value set to null when there's nothing to report.

This makes the response shape stable regardless of how much data we have on a given matched person, so client integrations can iterate over a fixed set of keys instead of conditionally checking for presence.

If your integration was using key presence ('fdy_outcome_xxx' in response) as a proxy for "did we get a score," update it to check for a non-null value instead.