As we know, in iOS you can add an email address to your Apple ID account, so that people can use it as another way to find and communicate with you on Apple services like FaceTime, iMessage, and Find My Friends.
the manual process to do is:
Sign in to your Apple ID account page.
Click Edit in the Account section.
Under Reachable at, select Add More.
Enter your additional email address and we'll send a verification to that address. Didn't get the email?
Enter the verification code and click Verify.
In Amex mobile app, they achieved to have a button click to start the process to add a credit card to apple pay without even need to leave the app.
we are building an app, each user will have his own email address. i am looking for a possiblity to have a button which allow user click to start the process step by step automatically add his email address as addtional Reachable to his current apple id account.