Setting the option `services.postgresql.enableTCPIP` to `false` did not
disable TCP/IP. Instead, this makes PostgreSQL listen on `localhost`.

This was confusing, as a security minded user may want to disable TCP/IP
entirely, even for localhost.

It also prevented running multiple instances of PostgreSQL on the same
host without manually assigning distinct TCP/IP ports.

This commit adds a new option, `services.postgres.listenAddresses`, that
defaults to `localhost`.

The default behaviour of `services.postgresql` is maintained: the
service listens on localhost using TCP/IP with the new default
`enableTCPIP = null`.

A warning informs users that setting `enableTCPIP = true` now only
listens on localhost. Setting `listenAddresses` is now required to
listen on all or multiple interfaces. This option follows the upstream
PostgreSQL syntax for `liste_addresses`.

Co-authored-by: Sandro <[email protected]>

Co-authored-by: Sandro <[email protected]>

Co-authored-by: Sandro <[email protected]>