Implement currency formatting with long display names.

[spookylukey]

Namely, things like:

"123,456.78 US dollars"

(en locale)

or

"dólares estadounidenses 123,456.78"

(es-GT locale)

The algorithm for doing this is described here: https://www.unicode.org/reports/tr35/tr35-numbers.html#Currencies and CLDR contains the data.

I'd be happy to attempt to implement this myself. Two issues I'm aware of:

1. What should the API be? An extra parameter to format_currency? A new format_type (this risks clashing with other format types already defined)?

2. It looks like this would require data not currently available in the pickled locale data. Specifically it requires the unitPattern data. I'm not sure how to go about adding this - apart from the import_cldr.py script, is there a specific process to follow?

For comparison, browsers currently implement this as part of Intl.NumberFormat using options {currencyDisplay: "name"}. In a browser console you can do:

> Intl.NumberFormat("en", {currencyDisplay:"name", style:"currency", currency:"USD"}).format(123456.78)
"123,456.78 US dollars"

[akx]

Heya! Yeah, this sounds like a good addition :)

Regarding locale data, there's no specific process. Just use common sense when coming up with the key within data to load the new data into – currency_unit_patterns sounds good, for instance.

API-wise, taking a cue from the JavaScript API, maybe format_type="name" would be a sane option? I don't think that'll end up clashing with any of the current formats (which seem to be standard, standard:short and accounting).

[spookylukey]

@akx - thanks so much for the reply. I'm not sure when I'll actually get round to this, but wanted to get things lined up for when I do have the time!