[FIX Modal] Use a more structured type for ModalOptions.afterSignUpAction
[FIX Modal] Use a more structured type for ModalOptions.afterSignUpAction

xtina-starr/reaction,artsy/reaction,artsy/reaction,xtina-starr/reaction,artsy/reaction-force,artsy/reaction,xtina-starr/reaction,xtina-starr/reaction,artsy/reaction-force