Add number truncation before back-end translation

[lucasscharenbroch]

Fixes #3102

When the front-end translate is called, all numbers are truncated to 2 decimal places.
The same was not true for the back-end translate, which seems to be the cause of this corner-case.

It appears that the Rust implementation of Fluent doesn't automatically do the truncation (before the comparison to [one] in FTL) according to the FluentNumberOptions (maximum_fraction_digits), while the JS version does. This is why my code explicitly rounds the number, where the TS only sets maximumFractionDigits.

[dae]

Thanks for looking into this Lucas!

There are a couple of things that would be nice to have:

• Instead of rebuilding the args into a new container, we could apply the transformation directly in the generated code. The strings.rs file we generate creates functions like this:

    /// {$count} cards added.
    #[inline]
    pub fn importing_cards_added<'a>(&'a self, count: impl Number) -> Cow<'a, str> {

        let mut args = FluentArgs::new();
        args.set("count", count.into());

        self.translate("importing-cards-added", Some(args))
    }

For numbers, we could call a function to modify them before calling .set(), and avoid the extra work.

• A small unit test that verifies things work correctly (i.e. if the fix is removed, the unit test starts failing) would be good. You could pick a random string from the generated code to test with.

[lucasscharenbroch]

Thanks, Dae!

I've made changes accordingly.

[dae]

Nice and clean - thanks again!