For example, give the fulfillment_orders/merged webhook:
{"merge_intents" =>
[{"fulfillment_order_id" => 1, "fulfillment_order_line_items" => []},
{"fulfillment_order_id" => 2,
"fulfillment_order_line_items" => [
{"id" => 111, "quantity" => 1}, {"id" => 222, "quantity" => 1}
]}],
"fulfillment_order_merges" => {"fulfillment_order" => {"id" => "gid://shopify/FulfillmentOrder/1", "status" => "open"}}}
fulfillment_order_line_items are for ID 2, which has been merged into ID 1. After the merge, fulfillment order 1 no longer contains those IDs and the fulfillment_order_line_item IDs that were move moved to ID 1 are completely different!
How to know what was merged?