User Story:

As a ARO developer, I want to be able to:

• Set the ManagedBy field for the Azure cluster resource group

so that

•  Automatic Azure RBAC plumbing can work.

Acceptance Criteria:

• The resource groups are created with the ManagedBy field set correctly.

Engineering Details:

• Setting the field requires the usual pipe to terraform from the install config. We need to add a new field and let the users set the value for the ManagedBy field.
• We need to add a new ManagedBy tag when creating the resource group here.
  https://github.com/openshift/installer/blob/3fe2ffb9cac587c6ad2a09b36f4d159e10489a2e/data/data/azure/vnet/main.tf#L30

This requires/does not require a design proposal.
This requires/does not require a feature gate.