Make fluent_number obey format specifiers for currencies

[Sh4rK]

Hi,

I just started to use fluent for python, and discovered that number format specifiers do not work for currencies.
Here's a small code snippet reproducing the issue:

from fluent.runtime import FluentBundle, FluentResource
from fluent.runtime.types import fluent_number

bundle = FluentBundle(["en"])
resource = FluentResource("amount = { $amount }")
bundle.add_resource(resource)

msg = bundle.get_message('amount')

amount = fluent_number(1, style="currency", currency="USD", minimumFractionDigits=0)
translated, errs = bundle.format_pattern(msg.value, {"amount": amount})
print(translated)  # Prints $1.00, expected $1.

Let me know if there's any issue with the patch!

[Pike]

Interesting topic. As we're talking currencies, @stasm, do you remember if we did anything about projectfluent/fluent.js#464 and the non-js impls?

As for this aspect of number formatting, I'm wary of exposing the number of digits to localizers for currencies. That doesn't sound like something that should be language specific. @stasm ?

Still, might be good to have a way for the programmer to control this.

[Sh4rK]

To clarify why I opened this PR and give some input:

The project we're working on is primarily for Hungarian audiences, but we're trying to localize it to a few other languages now.

I tried currency formatting as that's something we will need, and my problem is that Hungarian Forints (HUF) get formatted with 2 decimal places. That's unusual and unnecessary for most (common) use cases, as there's no fractional HUF in common use (the smallest value coin currently in circulation is 5 HUF, that's worth less than 0.02 USD).

Now, there are some areas that actually use fractional HUF, for example banking and probably other forms of accounting, and the ISO standard that seems relevant here specifies 2 decimal places, but in everyday life (stores, restaurants, online shops, services, etc.) it never appears.

Because of the above two different use cases I think there should be a way to customize the formatting, even if this is not the right one.

[Sh4rK]

Closing for lack of interest.