Add support for Nigeria's 11-character postcodes

[Adeniyikayodee]

NIPOST launched a new postcode for Nigeria in October 2026. It has 11 characters in five segments, for example EK-01-A03-FK-01: two letters, two digits, three letters or digits, two letters, and two digits. The two numeric segments run from 01 to 99.

NGFormatter accepted six digits only, so every new code was rejected. It now accepts both and formats the new code with hyphens, which is how NIPOST writes it. Six-digit codes are unchanged.

Format reference: https://docs.postcode.gov.ng/concepts/postcode-format

PHPUnit and PHPStan pass locally.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.21%. Comparing base (bd00669) to head (87e47a7).

Additional details and impacted files

@@            Coverage Diff            @@
##               main      #25   +/-   ##
=========================================
  Coverage     99.21%   99.21%           
- Complexity      502      503    +1     
=========================================
  Files           186      186           
  Lines          1019     1022    +3     
=========================================
+ Hits           1011     1014    +3     
  Misses            8        8           

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[Adeniyikayodee]

The Coding Standard job fails at composer install: squizlabs/php_codesniffer 4.0.1 is now blocked by a security advisory, so the check stops before it reads the code. The PHPUnit and PHPStan jobs pass. Happy to rebase once the tool is updated.

[Adeniyikayodee]

@BenMorel, I would be grateful if you could look at this whenever your time allows. Nigeria launched a new national postcode on 1 October, and the NG formatter still accepts only the six-digit code it replaces, so every new code is rejected. The format and its source are in the description, and the tests cover each segment. I am glad to change anything that would make this easier to merge. Thank you for maintaining this library, and please take it at your own pace.

[Adeniyikayodee]

A short update on the failing Coding Standard job: I ran ecs check locally with the same brick/coding-standard v4 config, and it reports no errors on src and tests for this branch. The job itself still stops at composer install for the reason above.

[BenMorel]

Thank you, @Adeniyikayodee!

The coding standard job has been fixed on main since.

[BenMorel]

Released as 0.6.3.

[Adeniyikayodee]

Thank you, @BenMorel, for the merge and the quick release.