It's not clear if I can use the San Francisco font to build a custom "sign in with apple" button. I want to build a custom button - following the human interface guidelines - but to do so, I would have to use Apple's SF font. But as far as I could find, the SF font is prohibited from being used in projects that are not mockups or sketchs. How can I build a visually custom Sign In with Apple button without using Apple's font?