Add overridable fields to the stream class

[s-vitaliy]

Part of SneaksAndData/kubectl-plugin-arcane#94

Scope

Implemented:

• Added the OverridableFields property to StreamClass

Checklist

• GitHub issue exists for this change.
• Unit tests added and they pass.
• Line Coverage is at least 80%.
• Review requested on latest commit.

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• Documentation updated (if applicable).

Note

Please add/change the user documentation in the usage.md and/or user_scenarios.md files.

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External dependencies

• Pull request contains changes in the custom resource definition models.
• Pull request adds the new stream definition layout version.

External dependencies checklist

• arcane-crd helm chart is updated accordingly and released.
• kubectl-plugin-arcane is updated with the new models.
• streaming plugins will be updated accordingly and released.
• arcane-stream-mock is updated and integration tests are passing.

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• This commit should be released in the next minor release.
• This commit should be released in the next patch release.
• This commit should NOT be released (e.g. documentation changes).

[github-actions]

go-test-coverage report:

Package coverage threshold (70%) satisfied:	PASS
Total coverage threshold (75%) satisfied:	PASS
Total test coverage: 88.3% (773/875)