Alertmanager URI might contain basic auth username & password, we should replace password with 'xxx' in logs and and error messages.
Go will still print it in HTTP request errors, but that will be fixed in the next Go release - https://go-review.googlesource.com/c/go/+/102855Fixes#259
This package adds handlers for different URI schemes, name clashes with http.Transport which is now passed around. Rename it to make it more obvious what it does
