Domains: Add Luhn check for SIREN/SIRET values

[eltongo]

Changes proposed in this Pull Request

This PR updates validation checks for .fr domains, to include a Luhn check on the SIREN/SIRET value provided by the user.

Testing instructions

• Run tests and make sure they pass (yarn run test-client "client/components/domains/registrant-extra-info/test")
• Add a .fr domain to cart
• After submitting the contact info, you will be asked "Who's this domain for?". Choose "Organization"
• Provide different values to the SIREN/SIRET field, and ensure that error messages appear when appropriate

This error should appear when the value is not valid (i.e. invalid characters or length):

This error should appear when everything else is OK, but the Luhn check fails:

[matticbot]

Test live: https://calypso.live/?branch=update/fr-siren-siret-checksum

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~252 bytes added 📈 [gzipped])

name      parsed_size           gzip_size
checkout       +521 B  (+0.0%)     +252 B  (+0.1%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[klimeryk]

Tested and works as expected 🎉

However, lonng-term we'll have to do this check on the backend instead, because that's what the new checkout uses. But in the meantime I'll be happy to get rid of the registration failures caused by invalid SIREN/SIRET numbers...

[klimeryk]

Hahaha, love that the old test used an invalid SIREN number and still passed :D

[a8ci18n]

This Pull Request is now available for translation here: https://translate.wordpress.com/deliverables/3502280

Thank you @eltongo for including a screenshot in the description! This is really helpful for our translators.