postinst does not add prometheus user

[Fabian Weisshaar]

The postinst script doesn't create the prometheus user. This makes the exporter unusable until prometheus user is created manually. I already fixed the bug upstream with https://salsa.debian.org/go-team/packages/prometheus-apache-exporter/merge_requests/1 and it's part of the 0.5.0+ds-2 bugfix release.

1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
Description: Ubuntu 18.04.1 LTS
Release: 18.04

2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
prometheus-apache-exporter:
  Installed: 0.5.0+ds-1
  Candidate: 0.5.0+ds-1
  Version table:
 *** 0.5.0+ds-1 500
        500 http://eu-central-1.ec2.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status

3) What you expected to happen
$ systemctl start prometheus-apache-exporter
starts the exporter

4) What happened instead
systemd[29960]: prometheus-apache-exporter.service: Failed to determine user credentials: No such process
systemd[29960]: prometheus-apache-exporter.service: Failed at step USER spawning /usr/bin/prometheus-apache-exporter: No such process