Validate Bulgaria natural persons internally

[Megamind51]

The European union API to validate TINs do not work for foreigners living in Bulgaria that have to submit a personal foreigner number. Given the API answer is the same as an incorrect TIN we can’t rely on it to verify Bulgarian TINs.
We fix this issue by setting BG TIN checks for natural-persons in tin-validator with validateInternally: true, forcing to run your internal check instead of European union API call.

Ticket:
https://uphold.atlassian.net/browse/BKO-6360

[Copilot]

Pull request overview

This PR addresses a validation issue for Bulgarian Taxpayer Identification Numbers (TINs) for natural persons. The European Union API does not properly validate TINs for foreigners living in Bulgaria with personal foreigner numbers, returning the same response as an incorrect TIN. The fix forces internal validation for Bulgarian natural person TINs instead of relying on the EU API, which aligns with the approach already used for several other countries.

Key Changes:

• Added validateInternally: true flag to the Bulgaria (BG) natural person TIN configuration

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[vitorcoxta]

LGTM to be moved to QA

[antoniogferreira]

LGTM!

Grant that tin from Bulgaria only check the amount of digits
Grant that tin from Bulgaria don't perform a check to VIES
Grant that others countries continue to be validated by VIES

[vitorcoxta]

LGTM!