Selective login for replicas

[shalomcrown]

Problem:
I have a replica with multiple masters.
I cannot set ACLs on these masters with different user names, for use with the replica, since there is no way of selectively authenticating against each of the masters.

Suggested feature
Extend the AUTH command to selectively authenticate against a given master, or add the user name and password to the REPLICAOF command

Alternatives
(since this is requested in the template)
I suppose it is possible to use the old style password system to have different passwords for different masters. However my project manager is concerned that he won't be able to use ACLs to restrict his web app to certain keys