databases/postgres_exporter: New port

[jbo]

Summary

PostgreSQL metric exporter for Prometheus.

PR: 276996

[tcberner]

Is there a reason no to use @sample?

https://docs.freebsd.org/en/books/porters-handbook/book/#plist-config

[jbo]

The section of the handbook you're referring to states:

If there is a very good reason not to install a working configuration file by default, only list the sample filename in pkg-plist, without the @sample followed by a space part, and add a message pointing out that the user must copy and edit the file before the software will work.

The configuration file consists pretty much only out of credentials and other user/installation specific information such as database names. The port cannot generate a working configuration file by default.
I'd argue that this is a very good reason :D

The pkg-message was has also been set:

A sample configuration file has been installed in
%%PREFIX%%/etc/postgres_exporter.yml.sample.

To use postgres_exporter, copy this config file to "postgres_exporter.yml"
and edit as needed, then enable and start the service: