Require templates to always include default stages
Currently all our
.gitlab-ci.yml templates are free to overwrite stages,
this results in very inconsistent behavior when you include another template,
as you pretty much always have to overwrite stages.
I think that we should aim to require that all templates, if they overwrite stages,
should follow the practice of adding
build, test, deploy. These stages are default
.gitlab-ci.yml if no stages is defined, so it should be fine to require them.
Enforce that all our templates do have a default set of stages.