[DPE-2646] - POC Rotate password

[MiaAltieri]

Issue

changes in password on config server aren't propagated to shard

Solution

update password passed on shard when config server password changes

Testing

juju deploy ./*charm --config role="config-server" config-server-one
juju deploy ./*charm --config role="shard" shard-one 
juju integrate config-server-one:config-server shard-one:sharding

# verify same password
juju run config-server-one/0 get-password
juju run shard-one/0 get-password

# verify cannot set shard password
juju run shard-one/0 set-password
juju run config-server-one/0 get-password
juju run shard-one/0 get-password

# verify setting config server password updates shard
juju run config-server-one/0 set-password
juju run config-server-one/0 get-password
juju run shard-one/0 get-password