refs #309, unmarshalling AutoDelete: "undefined" to false not true

[pafmaf]

exchange.auto_delete should not be undefined -> now defaults to false when it's string "undefined", not true.

• by default auto_delete is false
• when undefined, it's more likely to behave like false

Please see the details / origin of this change in #309 .
I could not find any explanation for the changes in #207 .

Why?

Sometimes there are issues with deploying exchanges using topology-operator. Unfortunately, it's a bit hard to reproduce, so I did not find the real problem yet. The exchanges are unchanged, and all set to auto_delete: false when being created, but the diff still says that auto_delete changed:

---

This is a draft, and I'm not sure how to test this, since I can only un-marshall the JSON, but setting up an exchange with undefined would require to "exploit a bug" in rabbitmq. (You shouldn't be able to create an exchange with auto_delete: undefined in the first place.)

---

If this change leads to problems for lib users, they should fix the original problem -> it may lead to fixes in rabbit? idk.

[pafmaf]

https://github.com/michaelklishin/rabbit-hole/actions/runs/9272433603/job/25753640675?pr=312#step:8:26

I can make the same test fail locally when running tests against the rabbitmq:3.13-management docker image (on main). So I don't think this is an issue with this PR.
It's still fine with 3.12 .

Not sure why it didn't break before though. - But maybe the 3.13 docker tag was overwritten somewhere in between and the newer versions cause problems.