Pull request title: modify requestPermissions method to open SFSafariViewController to comply with AppStore requirements
Comment: Apple testers rejected an app that uses Venmo API, because authorization request session currently opens in Safari browser. Apple testers think that it is a bad user experience and required to implement it using SFSafariViewController instead, so a user doesn't have to leave an app to authorize access to their Venmo account.
Pull request title: modify requestPermissions method to open SFSafariViewController to comply with AppStore requirements
Comment: Apple testers rejected an app that uses Venmo API, because authorization request session currently opens in Safari browser. Apple testers think that it is a bad user experience and required to implement it using SFSafariViewController instead, so a user doesn't have to leave an app to authorize access to their Venmo account.