Hi,

in order to load test our FCM connector, it's needed to replace the actual FCM backend w/ some bogus code/mock written in any language.

I've started on this to be able to change the FCM URLs:
https://github.com/matzew/aerogear-unifiedpush-server/commit/08d782ae52c04a5e693da0f87b77e2d11de24cf0

Now, besides just System properties, I think it would be handy to have this on our docker image as a ENV as well, so it's easy to spin up testing containers and use other container for the dummy load.

any thoughts ? 
-Matthias

--