Support for managed identity in Azure to fetch protected assets from Azure Storage

1. Proposed title of this feature request
Support for managed identity in Azure to fetch protected assets from Azure Storage

2. What is the nature and description of the request?
Ignition has support for IAM roles in AWS and thus can work with protected assets in AWS S3. Similar/same capabilities are requested/required in Azure, so that user-assigned managed identity would allow to fetch protected assets from Azure Storage

3. Why does the customer need this? (List the business requirements here)
Ignition files, may contain private/critical information about a OpenShift 4 - Cluster and thus are required to be protected, not only via IP access control but actually via Azure Managed Identity capabilities to only allow access for resources that have been authorized.

4. List any affected packages or components.
RHEL CoreOS, Ignition, Installer