fix: add test for optimistic locking and fix it

[ctron]

The reason for updating to Rust 1.76.0 was the introduction of inspect_err, which I find super helpful (also in this case):

operation().
    .inspect_err(|err| {
        log::info!("err: {err:?}");
    })

[jcrossley3]

I expected to see inspect_err called somewhere in here. 😄

[jcrossley3]

Curious why this is better?

[ctron]

Because otherwise tests will fail. Having init will run that methods twice (for two different tests) and the second one will fail. That's why the CI just failed, because the logger was already initialized by the first test.

[ctron]

I expected to see inspect_err called somewhere in here. 😄

I used that, but just for debugging. I removed it afterwards.

However, it allows one to more easily inject that into the call flow. Vs ripping it out and handling it with a match or if.