I've gone through most of the docs, and it looks like in order to route somewhere I need an upstream defined. The use case I'm trying to see if it's possible is to set a header like a host header and have the value in the header be sent to an SDS to resolve targets. Maybe this could be considered a dynamic upstream? Based on what I'm reading in the documentation it seems like when using the host header it needs to be resolved from a set of static things I've already defined.