Adds 'eventarcpublishing' as required API to custom event function (#1300)

Adds `eventarcpublishing.googleapis.com` as a required API for the `onCustomEventPublished` trigger so that the CLI enables it on deployment. Attempting to deploy a cloud function to GCF that listens on a non-existent channel will throw an error; `eventarcpublishing` API is necessary to allow the CLI to create the channel before the function is deployed.

Author: blidd-google

CHANGELOG.md

@@ -1,2 +1,3 @@
 - Allow Functions to specify vpcConnector as a string parameter (#1329)
 - Upgrade jsonwebtoken to version 9 (#1336)
+- Adds 'eventarcpublishing' as required API to custom event function

src/v2/providers/eventarc.ts

@@ -225,5 +225,12 @@ export function onCustomEventPublished<T = any>(
 
   func.__endpoint = endpoint;
 
+  func.__requiredAPIs = [
+    {
+      api: "eventarcpublishing.googleapis.com",
+      reason: "Needed for custom event functions",
+    },
+  ];
+
   return func;
 }