use apline from docker-registry.wikimedia.org

See merge request !4

This change uses alpine from docker-registry.wikimedia.org. Old alpine
image is not present on list of allowed images.

allowed_images: Allow subdirs in image paths

See merge request !3

Adds `/**/` to wildcards for:

  - docker-registry.wikimedia.org/**/*
  - registry.gitlab.com/gitlab-org/**/*

According to doublestar documentation[0], this matches zero or more
directories.

[0]. https://github.com/bmatcuk/doublestar#patterns

See also:

  https://gerrit.wikimedia.org/r/c/operations/puppet/+/805247/

Bug: T310535

Restrict images

See merge request !2

Adds allowed images parameter in order to restrict images allowed in
gitlab-ci.yaml

Bug: T297426

maximum_timeout: needs to be at least 10 minutes

Bug: T297426

add helm diff and helm install as CI jobs

See merge request !1

Bug: T297426

Bug: T297426

Bug: T297426

This adds basic terraform code to provision a managed Kubernetes
cluster on Digital Ocean.

Bug: T297426