CloudEvents validation with APIM

cloudevents-options-apim.xml

<inbound>
    <base />

    <!-- Get the WebHook-Request-Origin -->
    <set-variable value="@(context.Request.Headers.GetValueOrDefault("WebHook-Request-Origin"))" 
        name="webhookRequestOrigin" />

    <!--
        Return the response with the allowed origin
        and allowed rate to confirm the subscription.
     -->
    <return-response>
        <set-status code="200" reason="OK" />
        <set-header name="WebHook-Allowed-Origin" exists-action="override">
            <value>@((string)context.Variables["webhookRequestOrigin"])</value>
        </set-header>
        <set-header name="WebHook-Allowed-Rate" exists-action="override">
            <value>*</value>
        </set-header>
        <set-body />
    </return-response>

</inbound>