We want to:
- make the ci build the image (through  which sounds sensible enough)
- out of a tag (like we do the other modules either swh or swh-dependency package)
- out of a commit on master (tests ok then push with tag "latest")
- Make the job declaratively installed out of the swh-jenkins-jobs declarations
- Figure out how to create a swh-ci account and register it to the organization
(email: firstname.lastname@example.org; login: swh-ci, ...). For now we stuck with
one user of the organization since there is quite some limitations on that number (3).
swh organization on dockerhub: softwareheritage
Note: To be able to login, one user should be part of the organization.