Add UI Line Item Sequence / Order to the API Available Properties

[maddyp]

The API is unable to access a deal's line item order as displayed in the UI. This causes issues whenever the line item order is important and the API is used to create a deal with items, add line items to existing deals, or use the line items API to get data.

My company pushes the line items to other services when the deal is closed. It's confusing to the user when the items are rearranged and can require additional time for reordering. Additionally, if you're using a third-party integration for quoting (ex. PandaDoc), you'll run across this issue. 

Note:

The sequence can somewhat be obtained by using the line item ID. This only works if items are added manually, in the correct order, and after the deal has been created. If you add items when creating the deal those items are given IDs in the opposite order they were added. This was proposed as a solution to a different post. It isn't applicable here.