Failover capabilities for Connector/R2DBC

Goal is to permit setting some failover capability on connector level.

Configuration must permit setting multiple hosts/ports. Then, when trying to establish a connection, connector will trying to connect those hosts sequentially until success or throwing error if last host connection fails.

This would permit failover on multiple maxscale instances, avoiding use additional tools that monitor maxscales state.

R2DBC spec follows RFC3986, pemitting multiple host in connection String with the folowing format :
authority = [ userinfo "@" ] host [ ":" port ] [ "," host [ ":" port ] ]