Experimenting with more structured ways to handle command-line input/output in Rust

Convert fluent variable references to snake case

This is more in-line with rust style, however it does make it harder to search between both rust and fluent source files. It may be worth mandating fluent source matches rust style, so things are more consistent, and raise a warning at the macro level if this is not the case.

Created by  finchie  on February 14, 2024
4XADHKM66YB7R2AWXJAYR3N7CG3EM323S5WVTJWUDILZS3TAMYRAC
Change contents