Add token file reload to client library requirements

[liggitt]

Which issue(s) this PR fixes:

Fixes kubernetes/kubernetes#68164

Status of existing client libraries applying this change:

• periodically reload InClusterConfig token kubernetes-client/python#616
• client should periodically reload InClusterConfig token kubernetes-client/javascript#317
• client should periodically reload InClusterConfig token kubernetes-client/haskell#54
• client should periodically reload InClusterConfig token kubernetes-client/csharp#293
• client should periodically reload InClusterConfig token kubernetes-client/ruby#47
• client should periodically reload InClusterConfig token kubernetes-client/java#652
• client should periodically reload InClusterConfig token kubernetes-client/perl#12 (no inclusterconfig or tokenfile support yet)

/cc @mikedanese @zshihang @deads2k @lavalamp

[k8s-ci-robot]

@liggitt: Adding label: do-not-merge/blocked-paths because PR changes a protected file.

Reasons for blocking this PR:

[The Design Proposal process has been deprecated in favor of Kubernetes Enhancement Proposals (KEP). These documents are here for historical purposes only.]

• contributors/design-proposals/api-machinery/csi-new-client-library-procedure.md

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-ci-robot]

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[liggitt]

huh... is there a replacement location for this doc I'm missing?

[zshihang]

/lgtm

[mrbobbytables]

@liggitt Theres a blockade rule for all of design-proposals as they've been deprecated and replaced by KEPs. Ideally information from there gets integrated into various documentation in the devel directory.

[liggitt]

I'd like to override the blockade for this update, since this file is still getting actively referenced for new clients (xref https://groups.google.com/g/kubernetes-sig-api-machinery/c/9TT-7_WMPCE/m/GV3VJNluBQAJ)

follow up to move it to a more visible / current location seems good as well.

[mrbobbytables]

Done 👍

[ahmetb]

Is the reloading actually implemented in client-go? The rest.InClusterConfig() which is referenced from some client-go/examples seems to be still reading the token file only once.

[liggitt]

Is the reloading actually implemented in client-go? The rest.InClusterConfig() which is referenced from some client-go/examples seems to be still reading the token file only once.

yes, it plumbs both the value read and BearerTokenFile into the resulting config. When BearerTokenFile is set, it drives reloading behavior