Customizing router template

[carlomontanari]

Hi all,
I need to customize my routes with some parameters not supported by standard annotations.
For example I want to add some custom headers, change some buffer size and so on.
On OKD3 I used to modify haproxy-config.template (https://docs.okd.io/3.11/install_config/router/customized_haproxy_router.html#using-configmap-replace-template), but on OKD4 things are more complicated because the ingress is now configured by the operator.
Do you know how can I do the same kind of operation on OKD4?
Has anybody done some "advanced" configuration of the ingress behaviour on OKD4?

Thanks in advance