End user wanted to simulate Gateway timeout, so that they can implement a retry step in their process. We have a DEV endpoint which I changed to below.  This helps simulating the timeout.

<policies>
<inbound>
<base />
<return-response>
<set-status code="504" reason="Gateway Timeout" />
<set-header name="Content-Type" exists-action="override">
<value>application/json</value>
</set-header>
<set-body>@{
                return "{\"error\": \"Synthetic 504 for testing\"}";
            }</set-body>
</return-response>
</inbound>
<backend>
<base />
</backend>
<outbound>
<base />
</outbound>
<on-error>
<base />
</on-error>
</policies>