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This merge request introduces a client for Azure Blob Storage in
Workhorse. Currently customers wanting to use Azure Blob Storage have to
set up a Minio Gateway
(https://docs.gitlab.com/charts/advanced/external-object-storage/azure-minio-gateway.html),
which isn't ideal because it requires customers to maintain their own
proxy server for Azure. We have a number of customers who want native
support for Azure Blob Storage.

Unlike AWS and Google, Azure needs to use an Azure client inside
Workhorse to support direct uploads. Using standard HTTP transfers with
pre-signed URLs with the Azure Put Blob API
(https://docs.microsoft.com/en-us/rest/api/storageservices/put-blob)
doesn't work because Azure doesn't support chunked transfer encoding.
However, Azure does support uploading files in segments via the Put
Block and Put Block List API
(https://docs.microsoft.com/en-us/rest/api/storageservices/put-block),
but this requires an Azure client that can speak this API.

Instead of embe...