feat: add GCP Cloud Functions trigger with native auth

[walsm232]

Overview

Add a dedicated trigger type for invoking GCP Cloud Run Functions with built-in support for GCP authentication via Workload Identity and explicit service account JSON keys.

Unlike the generic HTTP trigger, this trigger uses Google's idtoken library to acquire and inject GCP ID tokens into requests, enabling authenticated invocations without any additional token management.

Checklist:

• My organization is added to USERS.md.

Testing

• Deployed a Cloud Run function on GCP and configured a GCP service account key as a Kubernetes secret, then triggered it end-to-end from a sensor using both the credentialSecret and Workload Identity auth modes.

{"level":"info","ts":"2026-02-16T22:08:07.295869754Z","logger":"argo-events.sensor","caller":"gcp-cloud-functions/gcp_cloud_functions.go:169","msg":"invoking GCP Cloud Function...","sensorName":"gcp-function-sa-key","triggerName":"invoke-function","triggerType":"GCPCloudFunctions","url":"https://argo-events-testing-<MASKED_ID>.europe-west1.run.app"}
{"level":"info","ts":"2026-02-16T22:08:08.277221172Z","logger":"argo-events.sensor","caller":"sensors/listener.go:449","msg":"Successfully processed trigger 'invoke-function'","sensorName":"gcp-function-sa-key","triggerName":"invoke-function","triggerType":"GCPCloudFunctions","triggeredBy":["test-dep"],"triggeredByEvents":["ce3a3aa35231481091bf1084123611c6"]}

Cloud Function is just configured with:

const functions = require('@google-cloud/functions-framework');

functions.http('helloHttp', (req, res) => {
  console.log('Received request:', JSON.stringify(req.body));
  res.status(200).json({
    status: 'ok',
    received: req.body
  });
});

and logs:

POST 200 197B 46ms Go-http-client/2.0 https://argo-events-testing-<MASKED_ID>.europe-west1.run.app/
Received request: {"message":"hello"}

Notes

• The credentialSecret field name and semantics follow the existing GCP PubSub event source convention
• First contribution to argo-events, happy to adjust anything to match project preferences. Let me know if I'm missing anything!

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