Transform Map - Prevent Priority Update unless on Insert - Pull 1

[hanna-g-sn]

PR Description:

Prevents priority churn during recurring imports. The onBefore Transform Map script computes priority from impact and urgency only for inserts. On updates it leaves priority unchanged to preserve service desk edits. Includes README and the script.

Pull Request Checklist

Overview

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• I have read and understood the CONTRIBUTING.md guidelines
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Code Quality

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Documentation

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