Explanation
Microsoft.Devices.DeviceCreated: Published when a device is registered to an IoT hub.
The first thing you want to do is handle Microsoft.EventGrid.SubscriptionValidationEvent events. Every time someone subscribes to an event, Event Grid sends a validation event to the endpoint with a validationCode in the data payload.
Reference:
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-event-grid
https://docs.microsoft.com/en-us/azure/event-grid/receive-events