Handle base paths #48
Description
It's possible that an upstream API may or may not be served from a base path (e.g. /stac)
It's also possible that the proxy may or may not be desired to be served from a base path (e.g. /, despite upstream being /stac).
We should be able to support any of these scenarios, independent of what the other server is doing (ie serve data from the proxy at / even if the upstream is served from /stac, or serve data from /stac even if the upstream is served from /).