Allow usage of if-empty, if-unused parameters for queue deletion

[jdfresser]

This closes ##747

Note to reviewers: remember to look at the commits in this PR and consider if they can be squashed
It probably misses some tests in https://github.com/rabbitmq/messaging-topology-operator/pull/759/files#diff-5619a2073d5cfff0b764ead1f1323f7554a40d748c906bcaa1322f1dd8a649dfR103

Summary Of Changes

• Support 'failsafe' strategies to prevent the operator to delete queues with consumers/messages
• Modifies the API with two new 'mutables' fields in Queue CRD: Spec/DeleteIfEmpty & Spec/DeleteIfUnused
• For Quorum queues, check the rabbitMQ HTTP API to know if there are consumers/messages
• For other queues, use the built-in parameters

[vmwclabot]

@jdfresser, you must sign our contributor license agreement before your changes are merged. Click here to sign the agreement. If you are a VMware employee, read this for further instruction.

[vmwclabot]

@jdfresser, we have received your signed contributor license agreement. The review is usually completed within a week, but may take longer under certain circumstances. Another comment will be added to the pull request to notify you when the merge can proceed.

[Zerpet]

Thank you for this contribution! I had a quick look and it's looking good overall. I want to check something with the team, because I'm unsure why Quorum Queues do not support if-empty and if-unused. Perhaps we could add that to the core, and that would simplify a lot this PR.

[jdfresser]

@Zerpet, Thank you for your review, I applied the suggested changes.

I want to check something with the team, because I'm unsure why Quorum Queues do not support if-empty and if-unused. Perhaps we could add that to the core, and that would simplify a lot this PR.

I'm also curious about the reason. Yes, better to avoid work-aroundsif we can!

[Zerpet]

Looking good, I'm going to do some manual QA before merging.

[Zerpet]

@Zerpet, Thank you for your review, I applied the suggested changes.

I want to check something with the team, because I'm unsure why Quorum Queues do not support if-empty and if-unused. Perhaps we could add that to the core, and that would simplify a lot this PR.

I'm also curious about the reason. Yes, better to avoid work-aroundsif we can!

@jdfresser the main reason is that we can't deliver on either promise without some racy conditions. In QQ, a publisher can publish to any member (usually 3) and a consumer can consume from any replica. This fact makes it harder to deliver on "if empty" or "if unused" without some limitations. It' not the same case for classic queues, CQ can deliver both promises.

FYI I opened this issue to support "if empty" and "if unused" in QQs, but it won't make it until rabbit 4.0: rabbitmq/rabbitmq-server#10543

[Zerpet]

CI failed because there are unused imports in internal/queue_delete_options.go. It fails to build and go vet. Can you fix those?

[jdfresser]

Sorry, stup*d me forgot to remove unused imports and to check local-tests results.

Local-tests are running well now.

[vmwclabot]

@jdfresser, VMware has approved your signed contributor license agreement.