POS Promotion Flow (promotion by multiple items)
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- clear existing promotion items
- loop item_details and push 'item_id' and 'quantity' to item_arr[]
- sent ajax request to 'AjaxPosPromotionTrait.php' which include datetime, customer_id, item_arr

AjaxPosPromotionTrait.php

- query available promotions.
- loop available promotion with item_arr.
- if the promotion is match , add item to 'match_items[]' and add promotion value & match_items[] to '$this-promotions[]'. 
- return '$this->promotions[]' .

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SO > INV > GIN Flow
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regarding this flow,there will be 2 ways to create. 
- 1 SO > 1 or multi GIN > 1 or multi INV
- Multi SO > 1 or multi GIN > multi INV 

- I created one more table to record SO_items 'good_issue_note_item_detail'.
- for duplicated so items, i saved in good_issue_note_items table group by item_id. 

eg . SO-22/0001 (ItemA - 30qty) , SO-22/0002 (ItemA - 20qty) , SO-22/0003 (ItemA - 10qty)
        if user create above SOs in same time (multiple SO), i recored below.
            - good_issue_note_items >> ItemA - 60 quantity
            - good_issue_notoe_item_detail  >> Item A , 30qty , so_id , so_detail_id
                                            >> Item A , 20qty , so_id , so_detail_id
                                            >> Item A , 10qty , so_id , so_detail_id
    
    User will see Item A - 60 quantity when create GIN . If he fill up GIN QTY , gin_qty will fill up in both 'good_issue_note_items' and 'good_issue_notoe_item_detail'.
    With that way, We can process SO multiple flow. 


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Need to watch
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- ItemTransaction (sometime itemtransaction not recorded properly. I fixed it and hope everything fine. But still need to watch).
- GLTransaction (sometime GLTransaction not recorded properly according to wrong user input).