test(pi): initialize stream provenance fields

Author: schickling

src/pi_channel.rs

@@ -250,6 +250,9 @@ mod tests {
                 tags: Vec::new(),
                 priority: None,
                 idempotency_key: None,
+                stream: None,
+                event_id: None,
+                event_key: None,
                 body: "Please verify the staging deploy.".into(),
             },
             "h.worker",