Regularly build images to pull in security patches from Base Image

[albuch]

Currently images are only build once a new release is deployed, however the used Alpine base image is regularly updated with the same tag when security patches for installed packages become available.
For kiam v4.0 the used base image build is from Dec 19th 2020 and there are currently 7 security vulnerabilities in the kiam image that have patches available if the image would be rebuilt, 4 of them being high severity issues.

Docker Hub has the configuration option to rebuild the image every time the base image is updated. I don't know though if quay.io supports the same concept. An alternative is to run a nightly build that pulls base images and pushes updated kiam images.