At the moment, RestContext.SetHeader(string value) (3_Game/http/restapi.c) can only be used to set the content type. I suggest to change it to SetHeader(string value, string header = "content-type"). This way, it stays backwards compatible, and with a simple if clause, arbitrary headers could be set.

I need this because I'd like to query a REST endpoint that requires things like X-Api-Key-Id.