feat: add support for CSI volumes

[mwritescode]

Fixes #11069

Description

This feature introduces support for Container Storage Interface (CSI) volumes in Knative Serving, enabling users to integrate with a wide variety of storage solutions through the Kubernetes CSI standard. This enhancement allows Knative services to leverage enterprise storage systems, cloud provider volumes, and other storage implementations that support the CSI specification, while maintaining Knative's serverless principles.

Proposed Changes

• Add support for CSI volume type in Knative Serving
• Enable users to mount CSI volumes into their Knative service containers
• Update relevant documentation and examples to include usage of CSI volumes
• Add feature flag control for CSI volume support

Release Note

Adding support for CSI (Container Storage Interface) volumes. This feature allows users to mount CSI-compatible storage volumes into their Knative service containers. It enables integration with enterprise storage solutions and cloud provider storage services that implement the CSI specification. The feature is behind the flag `kubernetes.podspec-volumes-csi`.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: dprotaso / name: Dave Protasowski (9dae83d)
• ✅ login: mwritescode / name: Martina Rossini (3380251)

[knative-prow]

Welcome @mwritescode! It looks like this is your first PR to knative/serving 🎉

[knative-prow]

Hi @mwritescode. Thanks for your PR.

I'm waiting for a knative member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

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-sigs/prow repository.

[dsimansk]

/ok-to-test

[dsimansk]

@mwritescode could you pls take a look literals syntax in tests?

[dsimansk]

@dprotaso @skonto what's your opinion on adding the support? Personally, I'd like to see a bit of e2e test coverage to confirm and ensure it's supportable from our point of view.

[dprotaso]

Personally, I'd like to see a bit of e2e test coverage to confirm and ensure it's supportable from our point of view.

@dsimansk Generally I don't want to have serving e2e tests to cover PodSpec features. K8s community would have coverage there and it would make the serving suite even slower to run.

I'm generally ok with stuff behind a feature flag because it's a buyer beware for teams that know what they are doing.

[dprotaso]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dprotaso, mwritescode

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [dprotaso]
• pkg/apis/OWNERS [dprotaso]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 3 lines in your changes missing coverage. Please review.

Project coverage is 75.03%. Comparing base (ad65df0) to head (9dae83d).
Report is 23 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/schema-tweak/overrides.go	0.00%	3 Missing ⚠️

❌ Your project status has failed because the head coverage (75.03%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15815      +/-   ##
==========================================
- Coverage   75.05%   75.03%   -0.02%     
==========================================
  Files         222      222              
  Lines       18074    18092      +18     
==========================================
+ Hits        13566    13576      +10     
- Misses       4158     4165       +7     
- Partials      350      351       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[dprotaso]

/override "codecov/project"

it's fixed in main

[knative-prow]

@dprotaso: Overrode contexts on behalf of dprotaso: codecov/project

In response to this:

/override "codecov/project"

it's fixed in main

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-sigs/prow repository.

[dprotaso]

/retest