Sync extensions between cluster members

[mpRegalado]

Describe the solution you'd like
Persistence for active extensions is only kept locally for each installation, so members of a cluster do not sync this configuration.

Describe alternatives you've considered
The configuration changes are saved in each installation to the local/extensions.conf file. Replacing the methods exposed in appserver/controllers/manager.py to preserve the endpoint but save the data to the kvStore should ensure persistence across members of a cluster.