Add Azure object storage support

Problem to solve

Currently we don't support Azure's object storage

Target audience

GitLab administrators

Proposal

• Gem: Fork fog-azure-rm to pull in updates needed for fog-core v2.1.2: https://github.com/fog/fog-azure-rm/pull/407
• Gem: Update fog-azure-rm to support direct upload calls
• Rails: Update direct upload code to work with fog-azure-rm: !38882 (merged)
• Rails: Add Azure configuration support: !38882 (merged)
• Rails: Support backups: !41649 (merged), !41626 (merged)
• Monkey patch CarrierWave to pull in Azure fixes: https://github.com/carrierwaveuploader/carrierwave/pull/2375, https://github.com/carrierwaveuploader/carrierwave/issues/2410
• Workhorse: Refactor S3Object and related classes to make it easier to add other providers: gitlab-workhorse!551 (merged)
• Workhorse: Add Azure SDK: gitlab-workhorse!555 (merged)
• Workhorse: Add Azure configuration support: gitlab-workhorse!555 (merged)
• Omnibus: Add Azure configuration support: omnibus-gitlab!4505 (merged)
• Charts: Add Azure configuration support: gitlab-org/charts/gitlab!1546 (merged)
• Runner: Add Azure support for cache: gitlab-runner!2366 (merged)

What does success look like, and how can we measure that?

Links / references

ZD https://gitlab.zendesk.com/agent/tickets/110434 (internal)