localeCurrencyName pipe incorrect translation

[michaelbromley]

Describe the bug
In the Admin UI we use the localeCurrencyName pipe to localize the names of currencies, e.g. in the currency select input of the Channel detail view.

In some languages, e.g. Russian, the displayed currencies include "not a number".

To Reproduce
Steps to reproduce the behavior:

1. Set Admin UI display language to Russian
2. Go to Channel detail view
3. Open the currency select dropdown
4. See list like this:
   

where "не число" means "not a number"

Expected behavior
Should not display "not a number"

Environment (please complete the following information):

• @vendure/core version: 1.1.0
• Nodejs version: any
• Database (mysql/postgres etc): any

Additional context
This is caused by a bad assumption in the pipe that passing undefined to the format() method will always output the string NaN:

vendure/packages/admin-ui/src/lib/core/src/shared/pipes/locale-currency-name.pipe.ts

Line 36 in ae07134

.replace(/\s*NaN\s*/, '');

There is a proper API to do this without hacky string replacement: formatToParts()

[michaelbromley]

Related note from Slack discussion:

One more interesting moment.
Because this api assume formating number, it tries to translate currencies as Genitive but not as Nominative declination.
Example:
Nan US dollars is transformed as US dollars - genetive plural. Nominative is "US dollar".
In Russian it works the same, but result is very strange to read.
"NaN российского рубля" is transformed to "российского рубля" - genetive not plural. Nomative (the aim) is "российский рубль".
In english using Genetive seems normal, but in Russian it seems as unquality translation.

Update:
Discovered the Intl.DisplayNames API which handles this correctly!

It can also be used for country names meaning we can remove all the manual translations of country names from all translation files, woo hoo!

[michaelbromley]

Related issue: the logic in the CurrencyInputComponent that determines whether to place the currency symbol before or after the number is broken for the same reason.