Add one-time code text content type to phone auth (#516)

Author: morganchen12

FirebasePhoneAuthUI/FUICodeField.m

@@ -59,6 +59,12 @@ - (void)setUpFromNib {
       UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
   self.inputField.userInteractionEnabled = YES;
 
+#if __IPHONE_OS_MIN_VERSION_REQUIRED > __IPHONE_12_0
+  if (@available(iOS 12.0, *)) {
+    self.inputField.textContentType = UITextContentTypeOneTimeCode;
+  }
+#endif // __IPHONE_OS_MIN_VERSION_REQUIRED > __IPHONE_12_0
+
   // Initialization code
   _codeEntry = [NSMutableString string];
 
@@ -165,10 +171,18 @@ - (CGSize)inputFieldIntrinsicContentSize {
 
 - (CGSize)intrinsicContentSize {
   CGSize textFieldSize = [self inputFieldIntrinsicContentSize];
-
   return textFieldSize;
 }
 
+- (UITextContentType)textContentType {
+#if __IPHONE_OS_MIN_VERSION_REQUIRED > __IPHONE_12_0
+  if (@available(iOS 12.0, *)) {
+    return UITextContentTypeOneTimeCode;
+  }
+#endif // __IPHONE_OS_MIN_VERSION_REQUIRED > __IPHONE_12_0
+  return nil;
+}
+
 @end
 
 NS_ASSUME_NONNULL_END