Incorrect finance Validation Logic

[lexendo]

Incorrect finance Validation Logic (possible bug)

Hi,
while reviewing the finance.py validators (ISIN, CUSIP, SEDOL), I found that the validators contain several issues, and I’d like to confirm whether this is a bug or if I’m missing something.

Reference to my mutation-testing analysis:
Bolest-oci/mutation-testing#35

F.e ISIN

The official ISIN format is two uppercase letters, nine alphanumeric characters, and one check digit (12 characters total).
However, the current validator seems incomplete:

• The Luhn checksum is implemented incorrectly and never computed.
• The format is not enforced (first two characters should be uppercase letters, last must be a digit).
• Lowercase letters and invalid characters are accepted.
• It does not verify that the first two letters form a country code (optional, but usually expected).

I'm thinking of submitting a PR with a fix, but I'm asking first to make sure I'm not missing something.
Thanks!