Cannot create event grid topic subscription for logic app standard workflow

Question

When deploying with vs code Logic App Standard extension a workflow with Event Grid trigger, a system topic is created with a valid subscription :

but when I try to do the same manually to understand how it works to automate it with Bicep , the subscription creation is failed with following error :

Webhook validation handshake failed for https://xyzxyz.azurewebsites.net/runtime/webhooks/workflow/scaleUnits/prod-00/workflows/xyzxyz/triggers/When_a_resource_event_occurs/paths/invoke. Http POST request retuned 2XX response with response body . When a validation request is accepted without validation code in the response body, Http GET is expected on the validation url included in the validation event(within 10 minutes)

for the endpoint url I use the url of the workflow :

how the extension calculate the workflow url used in the subscription?

Answer 1

just find a manual work arround and have to find a way to integrate it in my devops pipelines.
when adding the event subscription the workflow is fired with "validationUrl" event data , just copy/past on the browser and this will validate the subscription.