PostgreSQL 15 service

[Mauritz Stenek]

Hello,

On a full Guix system, I added the postgres service type like 
this:

```
(service postgresql-service-type
 (postgresql-configuration (postgresql postgresql-15)))
```

only upgrading to postgresql-15 from the default config (pg-10).

However, I get this error (verbatim):

```
# herd start postgres
Service user-homes has been started.
herd: error: exception caught while executing 'start' on service 
'postgres':
Throw to key `%exception' with args `("#<&invoke-error program: 
\"/gnu/store/m7dwq55l600g12bzm245zd9ha8v1zvn1-pg_ctl-wrapper\" 
arguments: (\"start\") exit-status: 1 term-signal: #f stop-signal: 
#f>")'.
```

Any ideas on how to fix this?

Thanks.

--
Mauritz Stenek <mstenek@disroot.org>