Deliverable 629871: [master] [UK] Payment Practices updates

[AleksanderGladkov]

What was done

• Added a new Reporting Scheme dimension (Standard / Dispute & Retention / Small Business) so the app can support country-specific payment practice rules without affecting existing W1/FR users.
• Implemented the UK (Dispute & Retention) scheme: dispute tracking, supply chain finance payment dates, and "% overdue due to dispute" reporting.
• Implemented the AU/NZ (Small Business) scheme: filters reporting to small-business suppliers and adds invoice count / value per period.
• Auto-detects the right scheme from the environment country on new reports, with an event for partners to override.
• Upgrade logic backfills the scheme on existing headers, so nothing breaks for current users.
• Surfaced the new fields and scheme selector on the relevant Payment Practice pages.
• Extracted shared test helpers into a new Test Library app and expanded unit tests across all three schemes.

Fixes AB#629871

Fixes AB#626294

[github-actions]

AL Documentation Audit

Documentation gaps were detected in the following apps:

• Payment-Practices-Test-Library: 0% documentation coverage
• Payment-Practices-Tests: 0% documentation coverage
• Payment-Practices: 10% documentation coverage

To generate documentation, run /al-docs init or /al-docs update using GitHub Copilot CLI or Claude Code.
This review is for awareness to help keep documentation in sync with code changes. It is okay to dismiss this request.

[github-actions]

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[ventselartur]

Please, review my comments