The current Patroni 3.2.2 has wired/flickering  behaviour:
it temporary flag pending_restart=True on many changes to REST API,
which is gone within a second but long enough to be cougth by charm.
Sleepping a bit is a necessary evil, until Patroni 3.3.0 upgrade.

The previous code sleept for 15 seconds waiting for pg_settings update.

Also, the unnecessary restarts could be triggered by missmatch of
Patroni config file and in-memory changes coming from REST API,
e.g. the slots were undefined in yaml file but set as an empty JSON {} => None.
Updating the default template to match the default API PATCHes and avoid restarts.

On topology observer event, the primary unit used to loose Primarly label.

The list of IPs were randomly sorted causing unnecessary Partroni
configuration re-generation with following Patroni restart/reload.

Housekeeping cleanup.

…hanged

Those defers are necessary to support scale-up/scale-down during the refresh,
while they have significalty slowdown PostgreSQL 16 bootstrap (and other
daily related mainteinance tasks, like re-scaling, full node reboot/recovery, etc).

Muting them for now with the proper documentation record to
forbid rescaling during the refresh, untli we minimise amount of defers in PG16.
Throw and warning for us to recall this promiss.

The current PG16 logic relies on Juju update-status or on_topology_change
observer events, while in some cases we start Patroni without the Observer,
causing a long waiting story till the next update-status arrives.

It is hard (impossible?) to catch the Juju Primary label
manipulations from Juju debug-log. Logging it simplifyies troubleshooting.

We had to wait 30 seconds in case of lack of connection which is unnecessary long.

Also, add details for the reason of failed connection Retry/CannotConnect.

It speedups the sinble unit app deployments.