Nested (i.e., dotted) field name support in #[tracing::instrument]

[anarchvile]

Motivation

I was reading the #[tracing::instrument] documentation, and noticed it mentioning that nested/dotted field names were not supported by the macro. However, I had code written and instrumented with #[tracing::instrument] macros where I was explicitly adding fields whose names were nested/dotted, and it all seemed to work fine/as-expected (i.e., the emitted spans had the correct field name and value, even with the dotted notation)...

Solution

Decided to simply amend the docs to reflect that the nested/dotted field names do seem to work as of today, and modified a unit test to exercise this accordingly? That being said, I may be missing some broader context/other nuances that actually prevent this from working as-intended. If so, just let me know, am more than happy to learn and take any further actions as necessary! 😅