Validate warnings in webhook unit tests

[sbueringer]

What would you like to be added (User Story)?

Note: This is a follow-up to: #8007 (specifically: #8007 (comment))

CR v0.15 extended the validating webhook interfaces to allow returning warnings. In the initial bump PR we just ignored the warning return parameter. Goal of this task is to extend our unit tests to validate that warnings are nil (as of today we never return warnings.

Detailed Description

The following commits shows all places where we adapted unit tests to ignore the warning return parameter: ea0dc4d

Anything else you would like to add?

No response

Label(s) to be applied

/kind cleanup
/area testing
One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

[sbueringer]

/triage accepted
/help wanted

[Dhairya-Arora01]

Is it correct that - "Gomega matcher should expect the warning To BeNil" ?

[sbueringer]

I would try BeEmpty. If possible we shouldn't care about the difference between nil and an empty slice

[Dhairya-Arora01]

@sbueringer , I would be happy to take this up

[Dhairya-Arora01]

/assign

[Dhairya-Arora01]

@sbueringer , "should we care about warnings being empty only in those cases where we don't expect any error ie expectErr is false "

[sbueringer]

Currently we expect all returned warnings to be empty except the 1-2 cases where we already validate that they are not.

Feel free to open a PR which only modifies on test file, then we can review this one and once we're good apply the same to everything.