feat: event ids, outbox identity migration

crates/event-payload/src/lib.rs

@@ -154,6 +154,16 @@ pub enum EventPayload {
     },
 }
 
+/// Wire form of an event: the tagged payload plus its optional identity.
+/// Messages without `event_id` (queued before identities existed) still decode.
+#[derive(Debug, Serialize, Deserialize, PartialEq)]
+pub struct EventMessage {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub event_id: Option<String>,
+    #[serde(flatten)]
+    pub payload: EventPayload,
+}
+
 impl EventPayload {
     pub fn event_type(&self) -> &'static str {
         match self {

crates/event-payload/tests/event_payload_test.rs

@@ -105,3 +105,29 @@ fn image_stored_event_type() {
     });
     assert_eq!(payload.event_type(), "ImageStored");
 }
+
+#[test]
+fn a_message_round_trips_its_event_id_and_decodes_without_one() {
+    use event_payload::EventMessage;
+
+    let with_id = EventMessage {
+        event_id: Some(Uuid::new_v4().to_string()),
+        payload: EventPayload::from(&review_logged()),
+    };
+    let json = serde_json::to_string(&with_id).unwrap();
+    assert_eq!(
+        serde_json::from_str::<EventMessage>(&json).unwrap(),
+        with_id
+    );
+
+    let legacy = serde_json::to_string(&EventPayload::from(&review_logged())).unwrap();
+    let decoded: EventMessage = serde_json::from_str(&legacy).unwrap();
+    assert_eq!(decoded.event_id, None);
+
+    let unit = EventMessage {
+        event_id: Some("x".into()),
+        payload: EventPayload::SearchReindexRequested,
+    };
+    let json = serde_json::to_string(&unit).unwrap();
+    assert_eq!(serde_json::from_str::<EventMessage>(&json).unwrap(), unit);
+}