support aad-pod-identity auth

[skriss]

Signed-off-by: Steve Kriss krisss@vmware.com

updates/replaces #29

closes #11
closes #12

[skriss]

cross-posting from the original PR:

@ezYakaEagle442 if you have bandwidth to test, I pushed two images: steveheptio/velero:aad-pod-identity and steveheptio/velero-plugin-for-microsoft-azure:aad-pod-identity. The former is only needed if you're using the restic integration. I did a quick test with them and it seems to be working properly, but I'd love to get more eyes and I still need to regression-test with SP auth.

I used a similar setup process to your script, but I used the following role assignment (based on our existing docs for SP auth):
--role "Contributor" --scopes /subscriptions/$AZURE_SUBSCRIPTION_ID

And then I manually added the aadpodidbinding label to the Velero pods (via the deployment & daemonset's pod template spec)

[skriss]

OK, I've successfully tested both aad-pod-identity auth and service principal auth using this code (including full backup and restore). This is now ready for review.

@ezYakaEagle442 I'm still very interested in having you test this as well.

[ezYakaEagle442]

@skriss hi, I was off a few days, I have a couple of priorities to manage first but I would be happy to help, I will do my best to test it asap, I will let you know my results

[skriss]

@carlisia @nrb PTAL (related to already-merged vmware-tanzu/velero#2602)