[US] ZIP Code Validation

Issue:

Incorrect ZIP code allowed when signing up.

Details to reproduce:

Sign up for Monzo using an address with a real ZIP code, but incorrect for given address.

Correct post code will not work for transactions requiring AVS. Incorrectly supplied postcode supplied does.

It appears no validation is being done on ZIP codes during sign-up.

OS: 12.4.1 (16G102)
Device: iPhone 6s Plus
App Version: 3.12.1 #584

Screenshots: