Resolve the External Values hooks this journey's validation rules compare against.

The journey runtime never calls external-values-api itself. A request names a datasource id declared by the saved journey config; the app and hook it resolves are read from that config, so a visitor cannot aim an installed app's integration at an arbitrary hook.

Requires a portal token: a hook call reaches the organization's third-party system, so it stays behind the identified-customer boundary. Public journeys skip these conditions.

Answers 200 whenever the request itself was valid, including when a hook failed — per datasource, so one unreachable system never fails the rules that did resolve.