OIDC support

[arbielsk]

Feature
Add support for OpenID Connect. This includes a new OidcTokenProvider which is able to refresh tokens. A new dependency is introduced in the form of IdentityModel.OidcClient.
While at it, I fixed a few typos in comments in src/KubernetesClient/KubernetesClientConfiguration.ConfigFile.cs

Motivation
At my company we are avid users of Bridge-To-Kubernetes which uses the C# K8S Client under the hood. We currently have multiple teams that are blocked from using Bridge-To-Kubernetes since the C# K8S client currently does not support OIDC. I therefore created this PR with the intent of adding OIDC support to C# K8S client so it can be integrated into Bridge-To-Kubernetes.

Disclaimer
I am not a C# developer. In fact this is the first C# code I have ever written. I therefore would like to ask for a thorough review; I am more than happy to update the PR to conform with any best practices, style guides and testing coverage as you see fit. I would be very grateful for any feedback!

I am also currently seeing the following warning and due to my unfamiliarity with C# I am unsure how to solve it optimally:

csharp/src/KubernetesClient/Extensions.cs(8,25): warning CA1724: The type name Extensions conflicts in whole or in part with the namespace name 'Microsoft.Extensions'. Change either name to eliminate the conflict.

Thank you for taking the time to review and consider this PR!
My team is very much looking forward to seeing this feature downstream in Bridge-To-Kubernetes as soon as possible, as this will significantly reduce our development efforts on multiple projects.

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[arbielsk]

CNCF ICLA accepted.

[arbielsk]

There seem to be non-deterministic tests in LeaderElectionTests.cs

Example
Run: https://github.com/kubernetes-client/csharp/actions/runs/468548275

Tests finish successfully for Ubuntu, but fail for MacOS with same code. On my local machine (MacOS) the tests run successfully (3/3 runs, no test failures).

Also without any code changes, the result for tests on the Ubuntu build differ between these two runs (I added an empty commit to re-trigger Github Actions):
https://github.com/kubernetes-client/csharp/actions/runs/468492411
https://github.com/kubernetes-client/csharp/actions/runs/468548275

I don't believe this is in the scope of this PR as it should be independent of the LeaderElection feature if I am interpreting the code correctly.

[tg123]

seems Microsoft.Extensions was introduce by new dependency

[arbielsk]

seems Microsoft.Extensions was introduce by new dependency

Yes it definitely was. However I am unsure what the correct resolution would be:

• Rename Extensions in K8S Client?
• Try to find a OIDC client that doesn't rely on Microsoft.Extensions (and is possibly lower quality)?
• Something I am not aware of?

Due to my unfamiliarity with C# I am also unsure on the possible implications of this conflict and the gravity of the warning.

[brendandburns]

Can you just use explicit full package names (e.g. k8s.Extensions) to eliminate the abiguity?

[tg123]

you may want rebase master to get rid of flaky testcases

i am fine with allow CA1723 in our repo, see kubernetes-client.ruleset in our repo.

[arbielsk]

Can you just use explicit full package names (e.g. k8s.Extensions) to eliminate the abiguity?

@brendandburns I've spent a little more time educating myself on the issue. As far as I understand the issue, the warning is produced because the type name Extensions in namespace k8s that has a partial conflict with the namespace name Microsoft.Extensions which is introduced by the OidcClient dependency. I therefore believe (with my limited knowledge of C#) that your suggestion is not applicable in this context as this is not about two type names being in conflict. If I am misunderstanding, I apologize.

I therefore understand that there are the following possible resolutions:

• accept the warning as suggested by @tg123
• rename the Extensions type to something different that seems appropriate. Maybe MetadataExtensions as the code seems to be related to that? I've tried renaming the class and file and the tests are still passing, including the VersionConverter Tests that are relying on this functionality.

@tg123 @brendanburns Please let me know what your preferred way of solving this would be. I have a commit prepared to rename the type name to MetadataExtensions but have not pushed it (yet), as I believe the strategy for handling this warning should be your call.

Thank you again for taking the time to review my PR!

[brendandburns]

Accepting the warning for now is fine with me.

If we want to make the change, we need to make it across a major version since it is a breaking change.

[tg123]

please add CA1723 to kubernetes-client.ruleset to disable warning
then LGTM

[arbielsk]

Thanks again, @brendanburns @tg123 for getting back to me so quickly. I've added CA1724 to the exceptions and added a comment explaining the situation.
Looking forward to seeing this merged :)

Thanks again and have a great night!

[tg123]

/LGTM

[arbielsk]

/assign @brendandburns

[brendandburns]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: arbielsk, brendandburns, tg123

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[arbielsk]

Thank you, @tg123, @brendandburns!