Complete PT regime and SAF-T addon

[cavalle]

This PR completes the PT regime and the SAF-T by adding:

• Product type extension
• European Article Number (EAN) identity
• Series and code format validation
• Validations for all required extensions
• Normalizations to set default codes for several extensions
• Support for foreign tax rates (i.e. customer-rates)
• A new stamp to store the full signature hash

Part of APP-101

Pre-Review Checklist

• I have performed a self-review of my code.
• I have added thorough tests with at least 90% code coverage.
• I've modified or created example GOBL documents to show my changes in use, if appropriate.
• When adding or modifying a tax regime or addon, I've added links to the source of the changes, either structured or in the comments.
• I've run go generate . to ensure that the Schemas and Regime data are up to date.
• All linter warnings have been reviewed and fixed.
• I've been obsessive with pointer nil checks to avoid panics.
• The CHANGELOG.md has been updated with an overview of my changes.
• Requested a review from @samlown.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.08%. Comparing base (00a47a1) to head (6c87de8).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #453      +/-   ##
==========================================
+ Coverage   84.57%   85.08%   +0.51%     
==========================================
  Files         250      254       +4     
  Lines       12348    12518     +170     
==========================================
+ Hits        10443    10651     +208     
+ Misses       1553     1518      -35     
+ Partials      352      349       -3     

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[samlown]

This is looking really nice! I've added a few suggestions that are worth discussing before merge.

[samlown]

BTW, I'd also aim for 100% test coverage if possible. I've been forcing myself recently, and feeling happier about it :-)

[cavalle]

BTW, I'd also aim for 100% test coverage if possible. I've been forcing myself recently, and feeling happier about it :-)

I also like large coverage as it often reveals issues you didn't anticipate. However, taken to the extreme, it forces to test certain logic in private functions that is there only as mere safeguards (cases that must not happen). I'm not always sure the effort of covering those cases is worth it. But I'll see if I can get to 100% here.

[cavalle]

100% coverage achieved!

[samlown]

🔝 🎩