[SR-Users] Programmatically modify SIP Requests/Responses in Kamailio

Hi, First of all I would like to congratulate and thank everyone who has worked in Kamailio. It looks like an awesome tool. I am starting a side project and I am not very familiar with Kamailio although I know SIP and VoIP in general, so I am more looking for answers that tell me if it's possible or not what I am asking along with some hints on how/where to look. Is there a way to filter/forward/modify(through the headers) incoming SIP requests and Kamailio SIP responses programmatically in Kamailio ? I have seen that you can run embedded code like Ruby, but I wonder if this is for simple things or more complex stuff which probably is in my case since there will be plenty of business logic to figure out what action to take with a SIP request. I have also found the EVAPI that is supposed to be handle events through TCP but not much more info available. So to sum up, is there a way to filter/forward/modify incoming SIP requests and create responses programmatically in Kamailio ? If yes, what's the proper way of doing that ? If no, any idea where I should look for that? Thanks, Filippos