`perform_enqueued_jobs` is a Sidekiq method.
Using this method violates the Dependency inversion principle[0].
This commit replaces `perform_enqueued_jobs` with ActiveJob's abstract
method `perform_enqueued_jobs` in specs.
[0]: https://en.wikipedia.org/wiki/Dependency_inversion_principle
Started implementation for the first iteration of
gitlab-org/gitlab-ce#32420. This will allow users to select a template
to start with, instead of an empty repository in the project just
created.
Internally this is basically a small extension of the ImportExport
GitLab projects we already support. We just import a certain import
tar archive. This commits includes the first one: Ruby on Rails. In the
future more will be added.
