User Profile

I have published an app on the App Store using my personal account which I would now like to transfer to a new separate developer account (which I also own). The app does not use iCloud, push notifications, or any in-app purchases. It does, however, use Sign In with Apple for user authentication. I have read the two Apple documents that pertain to transferring an app, but they go a little over my head, especially the user migration process. What is the user experience if I do not migrate users and simply transfer the app without handling this? Assuming the app handles expired authentication correctly, will they simply be asked to sign in to the app again and all will be well? Or will the user ID be different, meaning that "signing back in" will actually create a new account? In other words, is the user migration process only intended to minimize user inconvenience by maintaining logged-in sessions, or is it essential for user accounts to remain tied to their data? Thanks in advance for any advice.

I have a UITextView whose height I would like to limit to some reasonable value, with the text truncating if necessary. (scrolling is disabled). How can I make sure that the height of the text view matches that of the truncated content? If, for example, I set the height to a fixed value, there will some variable space at the bottom of the text view which will affect the layout of items below it. Is there some way to set a desired height, set and measure the truncated text, and then use that measurement to more precisely adjust the height? Is there even a way to measure the height of the displayed text within the UITextView?