The button allows to choose a ".gitlab-ci.yml" template that automatically
sets up the deployment of an application.
The currently supported template is Kubernetes template.
This commit builds on the groundwork in
ee008e300b1ec0abcc90e6a30816ec0754cea0dd, which refactored the backend
so the same code could be used for new dropdowns. In this commit its
used for templates for the `.gitlab-ci.yml` files.