Support time-limited Vault tokens in CI/CD integration
As an expansion on the Vault Proof of Concept, allow the user to simply obtain temporary Vault credentials at job start, and then manually use the vault CLI to request the desired secret. This will have advantages over https://gitlab.com/gitlab-org/gitlab-ee/issues/9981 and https://gitlab.com/gitlab-org/gitlab-ce/issues/61053 because:
- It doesn't require the requested secrets to be known at runner config time
- It doesn't requires the requested secrets to be part of the GitLab UI
- It allows the requested secrets to be treated "as code" in the
.gitlab-ci.yml
Edited by Jason Yavorska