Use GitLab CI multi target docker build image

Description

uis/devops/continuous-delivery/ci-templates#78 (closed) introduced a template to be able to build and publish multiple docker images. This task is to use that template.

Further details

Task list

• Merge Dockerfiles
• Use template to build and publish example and final stage containers

Acceptance criteria

• final stage published through normal pipeline build
• example stage built & published through the docker_build_targets

Links/references