Webhook notifications allow SAP Cloud ALM (CALM) to automatically push updates to your designated endpoints whenever specific events occur. This eliminates the need for constant polling and ensures that you receive information instantly.

Example: whenever there is a change of status of a Task, CALM will trigger a webhook with notification along with basic info about the change into an iflow in SAP Cloud Integration (SCI)

Here we will set up notifications related to Tasks, but the same setup works for other resources like Requirements, Defects and so on. 
The configuration needs to be done at 4 different places:

• Create webhook receiving iflow (SCI)

• Set Endpoint in Landscape Management (CALM)

• Create Webhook and Subscription in External API Management (CALM)

• Assign Subscription to Project in Implementation (CALM)

Create webhook receiving iflow

Create a simple iflow with HTTPS Sender adapter, which will serve as the notification endpoint. Deploy it, so that the URL is available. It can be something like like https://[tenant_address]. hana.ondemand.com/http/tasks_notifications
Note down the path /http/tasks_notifications, or whatever you named it, as this we will use later.

Endpoint in Landscape Management

Navigate to Administration -> Landscape Management and select the system to which you want to send your notifications, in our case it will be SAP Integration Suite (Cloud Integration).
Go to Endpoint tab and create an endpoint with Use Case External API Management.

To be able to set the authentication, you need to create a Service Key in BTP Cockpit. Copy-paste the credential information into the Endpoint configuration and now you have a working connection to SCI.

Create Webhook and Subscription in External API Management

Navigate to Administration -> External API Management. On the left pane you can see Subscriptions management and Webhooks management. Go to Webhooks management, as we first create a Webhook and then assign it to Subscription.

Proceed with configuration as per the screenshot. LMS Service and Endpoint is what we set up in previous step. As Path set the path of our notification iflow from step 1. No need to specify the full URL, as that will be taken from the Endpoint.

Resource Type determines the type of resource we want to be notified about. Nevertheless, the same webhook can be used for other resources as well.

Now let's create Subscription. Just toggle onto Subscriptions management on the left pane, create a Subscription and assign the Webhook, which we created before. Again, follow the screenshot. 

Assign Subscription to Project in Implementation

Navigate to Implementation -> Projects and Setup and select your project.
It is important to point out that you can set up notifications per Project. You can be notified by changes on Tasks belonging into one Project, but Tasks of other Project will not trigger anything.

Go to Subscriptions tab and there you can activate notifications for individual Item Type. See that we can assign the same Subscription to all Item Types, regardless of what Resource Type we selected in previous step. 

Test our notifications

Now everything is set up. Go to any Task within the Project, for which we activated notifications and perform a change, e.g. switch it to another status.
Navigate to Administration -> External API Management and select Console from the left pane. Refresh if necessary and you will see all your webhook traffic.
If everything has been properly configured, you also received the payload into your SCI notification iflow.

It was also published here:

https://community.sap.com/t5/technology-blogs-by-members/configure-webhook-notifications-from-sap-cloud-alm-to-sap-cloud-integration/ba-p/14037755