sanity checks 0.15.0

Please do your sanity checks according to the steps below:

1. Download the tarball, verify it is sane, build it and run tests.
   • tarball: https://gitlab.isc.org/isc-projects/stork/-/jobs/1544152/artifacts/browse
   • (older tarball: https://gitlab.isc.org/isc-projects/stork/-/jobs/1543747/artifacts/browse)
2. Start the demo with rake docker_up and follow the steps from: https://gitlab.isc.org/isc-projects/stork/-/wikis/Demo
3. Install server and agent locally e.g. on VMs from the binary packages:
   • debs and RPMs: https://gitlab.isc.org/isc-projects/stork/-/jobs/1544153/artifacts/browse
   • (older debs and RPMs: https://gitlab.isc.org/isc-projects/stork/-/jobs/1543748/artifacts/browse)

If you want you can execute GUI system test based on selenium with:

rake system_tests_ui BROWSER=Firefox
rake system_tests_ui BROWSER=Chrome

but they have not been run for a while, they might not pass.