Add MSI Support for Azure plugin.

[yanggangtony]

Thank you for contributing to Velero!

Please add a summary of your change

Add MSI Support for Azure plugin.

Does your change fix a particular issue?

Fixes #(#6931)

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

Merging #6938 (c8ffce8) into main (ed441de) will increase coverage by 0.01%.
The diff coverage is 57.14%.

@@            Coverage Diff             @@
##             main    #6938      +/-   ##
==========================================
+ Coverage   60.75%   60.77%   +0.01%     
==========================================
  Files         250      250              
  Lines       26632    26639       +7     
==========================================
+ Hits        16180    16189       +9     
+ Misses       9302     9299       -3     
- Partials     1150     1151       +1     

Files	Coverage Δ
pkg/util/azure/credential.go	69.41% <57.14%> (-4.95%)	⬇️

... and 1 file with indirect coverage changes

[yanggangtony]

@ywk253100
How about like this change?

[yanggangtony]

@ywk253100
thanks for quick review.
rebased.

[anshulahuja98]

@yanggangtony do you have an environment to test this?
Or should I test and update you.

Can you also make a PR for azure plugin consuming this, I'll pull the commit from your branch to test out in cluster.

[yanggangtony]

@yanggangtony do you have an environment to test this? Or should I test and update you.

@anshulahuja98
No , i have no azure env in my local test. your help to test is much appreciate.

Can you also make a PR for azure plugin consuming this, I'll pull the commit from your
branch to test out in cluster.

Ok , i will go to the azure plugin repo , and found the call to consume that .

---

There is seems some unit test wrong with func TestNewCredential(t *testing.T) {

[yanggangtony]

@anshulahuja98
vmware-tanzu/velero-plugin-for-microsoft-azure#212 .
Please help to test that in azure cluster.
Thanks.

[anshulahuja98]

@anshulahuja98 vmware-tanzu/velero-plugin-for-microsoft-azure#212 . Please help to test that in azure cluster. Thanks.

Ack
will test and get back.

[anshulahuja98]

Update: I tried to run some automated tests yesterday, but did some mistakes

will try again today, and get back once done.

[yanggangtony]

thanks .
@anshulahuja98

[anshulahuja98]

Just completed validation, it is working as expected.
@yanggangtony can you please check the failing tests in the CI. Also see if it is feasible to add test for this scenario.

[yanggangtony]

ok , i will check it later.

[yanggangtony]

i will continue test..
still show the errors..

[yanggangtony]

interesting!! @anshulahuja98
i debug the code , found the NewCredential will always return ok, not error shows..
but when you use it to GetToken , will shows the details errors.

[yanggangtony]

the ci happy now..

[anshulahuja98]

@yanggangtony please update the azure PR as well with latest reference

[yanggangtony]

Ack
@anshulahuja98