Always adding product extension to items, fix preceding validation

[samlown]

Changes

• The es-tbai-product is now added automatically to all items during normalization.
• TicketBAI validation was not correctly checking preceding data.

Checklist before requesting a review

• 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 the 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 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 81.49%. Comparing base (78ccade) to head (77efc61).
Report is 36 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #431   +/-   ##
=======================================
  Coverage   81.48%   81.49%           
=======================================
  Files         233      233           
  Lines       11491    11417   -74     
=======================================
- Hits         9364     9304   -60     
+ Misses       1764     1752   -12     
+ Partials      363      361    -2     

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[cavalle]

LGTM!