Sidekiq create deployment for preprod

Let us:

• learn our sidekiq subchart
• create the necessary deployment for preprod
  • We'll need secrets and lot's of them
• discover the hardships of manually maintaining the versioning of our helm chart

For a first iteration we'll use only the default subchart as-is, meaning we'll get the sidekiq-all-in-one deployment model.

/cc @jarv