Add the ability to use AAD groups

[mirthy]

What this PR does / why we need it: As per #1611, this adds the ability to use AAD groups and documents how to use it. The groups functionality is already built into AAD and it's just making sure it's turned on the Server Application AAD Manifest. Then, on the Kubernetes cluster side, it's just configuring the --oidc-groups-claim, which as no default, so it has to be set to groups for it read from AAD provided groups.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #1611

Special notes for your reviewer:

• This adds a parameter to to be included in the OIDC configuration, explicitly setting the groups claim --oidc-groups-claim to groups
• Updated the documentation to include how to use groups and mention the steps that are required.

Release note:

[msftclas]

All CLA requirements met.

[jackfrancis]

lgtm, thanks @mirthy !