[Feature] external-dns: support for workload identity

[weisdd]

Is your feature request related to a problem? Please describe.
external-dns still lacks support for Workload Identity.

Describe the solution you'd like
It'd be great if Microsoft can dedicate some resources to have external-dns gain support for Workload Identity.

Describe alternatives you've considered

• Implemented support for workload identity on top of adal library, which is still in use by external-dns: feat(Azure): add support for workload identity kubernetes-sigs/external-dns#3111:
  • it's a bit hacky, because adal cannot automatically re-read federated token from disk, so we need to have a little wrapper for refresh function;
  • the PR has stayed unreviewed since the 26th of October 2022;
• Waited for the PR that migrates Azure provider from adal to Azure SDK for Go to be merged: Update Azure SDK and remove deprecated autorest dependency kubernetes-sigs/external-dns#3040 - the library has native support for Workload Identity with proper token renewal process, so the functionality can be added to external-dns with just a few lines of code:
  • the PR was opened on the 22nd of September 2022, not really moving anywhere either;

Additional context
(I've created this issue as suggested by Microsoft during our monthly call today)

[weisdd]

For those who's interested in the functionality, I'm happy to say that we should see it in the next release. More details here: kubernetes-sigs/external-dns#3906

[weisdd]

It's available now in v0.13.6.

[weisdd]

@miwithro thanks for your help on Slack! :)