implement datastore that can be used by multiple epp replicas

[nirrozenbaum]

as of today, epp runs as a single replica.
if one wants to run multiple replicas for high availability, each replica will have it's own in-memory cache (datastore).
it should be possible to run multiple epp replicas with a single cache that all replicas access.
one such option would be to implement a redis based datastore.

additionsl aspect of having alternative datastore (not in memory) is fast recovery from failures

[kfswain]

I may close this in favor of the HA issue to centralize this discussion if that is acceptable @nirrozenbaum ?

[nirrozenbaum]

sure