feat: enable renaming meta fields

[atusy]

I want to rename meta data fields in JSON log so that I can align the names with logs from other products.

The syntax is just like dplyr::rename.

The example renames time to timestamp.

> logger::log_formatter(logger::formatter_json)
> logger::log_layout(logger::layout_json_parser(fields = c(timestamp = "time", "level", "ns", "fn")))
> logger::log_warn(message = "this is a warning")
{"timestamp":"2024-11-19 00:16:22","level":"WARN","ns":"global","fn":"NA","message":"this is a warning"}

[daroczig]

This is super cool, thank you 🙇

Could you please add that example to the function's docs and preferably to the unit tests (test-layouts.R) as well?

[atusy]

@daroczig
Thanks! I added the both :)

[daroczig]

thanks a ton 🙇