LG-7832: Support multiple characters for USPS transliteration

[NavaTim]

🎫 Ticket

• LG-7832

🛠 Summary of changes

• Support multiple characters to be returned from transliteration
• Test behavior around non-ASCII spaces

📜 Testing Plan

Provide a checklist of steps to confirm the changes.

• Complete IdV flow up to in-person state ID page
• Enter a character that converts to multiple characters into a name field (see mappings here)
• Enter an unsupported character (e.g. Cyrillic) into the same name field after that character
• Complete remainder of form
• Submit form
• Verify that form response identifies the unsupported character correctly

[tomas-nava]

approve!

before:

after:

I would recommend that you also edit line 88 in UspsInPersonProofing::TransliterableValidator to be

      (result.unsupported_chars + additional_chars).compact.sort.uniq

(adding .compact); I think your changes in this PR preclude this happening again, but I got a comparison of String with nil failed error on this line when creating the before screenshot above.

[NavaTim]

@tomas-nava Yes, the original issue was the cause of the nil value. This will prevent the nil from recurring.