Open
Description
It can be confusing to follow the code in pkg/alertmanager/multitenant.go, particularly with respect to what code and interfaces belong to the distributor, and what belongs to the alertmanager instance (this is quite apparent in #4928). I'd like to suggest splitting pkg/alertmanager as follows:
/pkg/alertmanager/distributor(can contain distributor.go and the contents of merger/)/pkg/alertmanager/instance
There might be other opportunities to cleanup too.