MSC4140: support filters on delayed event lookup (#5038)

* MSC4140: support filters on delayed event lookup

Support looking up scheduled/finalised delayed events, and looking up a
single delayed event.

* Add test coverage for delayed event lookup filters

* Prettier

* Use it.each for test loop

* Support multiple delayIds

* Support single or multiple delayIds

As it may be more common to look up a single delayed event than to look
up many of them, support passing a single delayID in the lookup function
instead of needing to pass a single-element array.

src/client.ts

@@ -3537,13 +3537,17 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
     }
 
     /**
-     * Get all pending delayed events for the calling user.
+     * Get information about delayed events owned by the requesting user.
      *
      * Note: This endpoint is unstable, and can throw an `Error`.
      *   Check progress on [MSC4140](https://github.com/matrix-org/matrix-spec-proposals/pull/4140) for more details.
      */
     // eslint-disable-next-line
-    public async _unstable_getDelayedEvents(fromToken?: string): Promise<DelayedEventInfo> {
+    public async _unstable_getDelayedEvents(
+        status?: "scheduled" | "finalised",
+        delayId?: string | string[],
+        fromToken?: string,
+    ): Promise<DelayedEventInfo> {
         if (!(await this.doesServerSupportUnstableFeature(UNSTABLE_MSC4140_DELAYED_EVENTS))) {
             throw new UnsupportedDelayedEventsEndpointError(
                 "Server does not support the delayed events API",
@@ -3551,7 +3555,11 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             );
         }
 
-        const queryDict = fromToken ? { from: fromToken } : undefined;
+        const queryDict = {
+            from: fromToken,
+            status,
+            delay_id: delayId,
+        };
         return await this.http.authedRequest(Method.Get, "/delayed_events", queryDict, undefined, {
             prefix: `${ClientPrefix.Unstable}/${UNSTABLE_MSC4140_DELAYED_EVENTS}`,
         });