support configmap delete

[huiwq1990]

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What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage
/sig storage

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

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Does this PR introduce a user-facing change?

other Note

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[rambohe-ch]

@huiwq1990 Very appreciate for making pull request. end user should not delete yurt-hub-cfg configmap because yurthub component on edge nodes may not work. if yurt-hub-cfg configmap is deleted accidentally, the feature of yurthub can not be guaranteed. so configmap delete event is not handled.

[rambohe-ch]

@huiwq1990 Very appreciate for making pull request. end user should not delete yurt-hub-cfg configmap because yurthub component on edge nodes may not work. if yurt-hub-cfg configmap is deleted accidentally, the feature of yurthub can not be guaranteed. so configmap delete event is not handled.

@huiwq1990 I'd like to add a new comment to reply. I think that maybe handle configmap delete event maybe is reasonable, because end user will find feature can not work after delete yurt-hub-cfg configmap. In the current process, even if yurt-hub-cfg configmap is deleted, the original setting feature still can work, it's not reasonable.

[rambohe-ch]

@huiwq1990 how about add configmap delete event handler for approver, you can dive into the code here:
https://github.com/openyurtio/openyurt/blob/master/pkg/yurthub/filter/approver.go#L73-L76

[rambohe-ch]

@huiwq1990 welcome you to apply OpenYurt community member. and the apply example is here: openyurtio/community#33

[rambohe-ch]

/lgtm
/approve

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: huiwq1990, rambohe-ch

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