The `postgresql-upgrade` script will now run any executables located in
the `/etc/postgresql/post-upgrade.d` directory. This will allow making
arbitrary changes to the system after a PostgreSQL major version
upgrade. Notably, we will use this capability to change the WAL-G
configuration to upload WAL archives and backups to the correct
version-specific location.
There's a bit of a dependency loop between the _postgresql-server_ role
and other roles that supplement it, like _wal-g-pg_ and
_postgresql-cert_. The latter roles need PostgreSQL installed, but when
those roles are used, the server cannot be started until they have been
applied. To resolve this situation, I've broken out the initial
installation steps from the _postgresql-server_ role into
_postgresql-server-base_. Roles that need PostgreSQL installed, but
need to be applied before the server can start, can depend on this role.
Dustin