We enabled ArcGIS Portal to facilitate cross-domain requests via Cross-Origin Resource Sharing (CORS). On the other hand, we are developing an iPhone app which is built as React Native APP (across iPhone and Android platforms) using ArcGIS Maps SDK for JavaScript. The APP's server API is hosted in another domain different from ArcGIS Portal's. The client APP is installed in a phone, but NOT web app opened from a website with domain.
So we are looking out for approach to do the coding to handle CORS in the APP while APP accesses ArcGIS Portal from client phone directly, but not via a server domain.
Could anyone suggest a list of options to work with ArcGIS Portal CORS in our use case?