Improvement: REST-API - Add List of Order Status Node

[magento-engcom-team]

According to: https://magento.stackexchange.com/questions/150492/magento-2-how-to-get-all-order-status there isn't a possibility to get all Order Status that were available inside the Shop.

For ERP Systems which would change the status from "open" to "complete" or a custom status it is necessary to know how the internal name of the status is setup inside the Shop to update an order from status A to status B.

For example:

• Inside Shop A there is a custom status "parts supplied", the internal status_name of this custom status is set to "custom_partssupplied".
• The Order was read with Status "open".
• After work is done in the ERP-System, this custom status "parts supplied" should be applied to this Order
• Over REST-API there is a possibility to update "status" with a string -> namely the internal status_name in this example "custom_partssupplied"

Problem now is:

• How to get the List of all status over REST-API without changing anything to the shop (changing php files)?

Most ERP-Systems using a proprietary connector, tool, php-toolbox to do this job, but that is against nature of an api: use the api, don't work around the api.

A Node to get all status from shop is needed to get this task done, but this Node is missing.

Original Report: magento/magento2#16324 by @DanielKarr87