ASM block page for use with API waf policy
Also keep in mind that ASM_REQUEST_DONE irule event will show you support id even for good requests, so if you want to insert the header only when there is violation then you can use ASM_REQUEST_BLOCKING as a replacement for ASM_REQUEST_DONE as it will trigger only for bad requests.
Just an update from me. I found a much much simpler way to accomplish this.
In the settings for the policy and under response and blocking pages, i edit and created a new header and just used the support id variable from the page on the header and that worked like a charm. No irules to apply or anything. 😄