Zendesk iOS SDK Custom User Fields

Hello, I have set up custom user fields that I would like to populate from the iOS Zendesk SDK. For example, I want to send metadata from my app and associate it with a user. 

I have been able to achieve this using Postman and hitting the API directly. However, with the SDK, the only two fields I see that are supported are name and email, unless I am missing something. Can anyone point me in the direction of how to do this using the SDK.