Add Authentication Endpoint to MSI Properties

[annzho]

Issue describing the changes in this PR

Including Authentication Endpoint in MSI Properties as bug fix for this work item.

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

[annzho]

Hi @pragnagopa, could you take a look at this PR? It's a small change with accompanying tests, just adding the AuthenticationEndpoint property to the ManagedServiceIdentity class

[annzho]

Hi @pragnagopa, just wanted to follow up - could you take a look at this?