Hi,

attached is a patch to make postgresql find its plugins. Actually, it
only makes it unable to follow symlinks, so we can provide a union of
postgresql and plugins to the postgresql service. I also attached an
example system configuration that shows how this works. Do you think
this is the right solution? The patch was taken from nixos and updated
for the current version of postgresql.

Note that the VM will have troubles loading the extensions with only
its 256MB memory by default. You should add more ram to it.

Inside the VM, you can test with:

psql -U postgres
> create database postgistest;
> \connect postgistest;
> create extension postgis;
> create extension postgis_topology;

no error, you now have an empty spatial database :)

An extension would be to have a procedure to build the union of
packages (postgresql and extensions) called by the postgresql service.
we would have an "extension" field that would contain a list of
packages that contain extensions for postgresql and the service would
build and use the union of postgresql and these extensions. WDYT?