fix(core): Clear previous line adjustments before testing order item promotions

[putermancer]

Description

OrderCalculator#applyOrderPromotions clears out all existing DISTRIBUTED_ORDER_PROMOTIONs before testing promotions. applyOrderItemPromotions does not currently do the same, the result of which is that when conditions / actions are encountered, previous adjustment data may be present on the line items in question.

My specific use case was when creating a promotion of the type "apply a bulk purchase discount, but only to items that aren't already discounted," e.g. when there are 10+ of a product and they aren't already discounted.

Without this change: upon reaching 10 items, the line items become discounted. Upon reaching 11 items, the test for "are there adjustments applied" returns true (the previous adjustment), resulting in the discount being removed. Bump the quantity to 12 and it applies again.

With this change: it works properly when reaching 10, 11, 12, and on.

Breaking changes

No.

Checklist

📌 Always:

• I have set a clear title
• My PR is small and contains a single feature
• I have checked my own PR

👍 Most of the time:

• I have added or updated test cases
• (N/A) I have updated the README if needed

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Name	Status	Preview	Updated (UTC)
docs	✅ Ready (Inspect)	Visit Preview	Jan 16, 2025 9:16pm

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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