Adding Sign In/Sign Up into rails app

I am trying to integrate SignIn / SignUp into my rails application.
Currently i have Two API's for Sign In and Sign Up (Maintained by other team). These API's will take care of validations and stuff at their end and send me success/failure response back.

I am aware that we can have a custom SignIn/SignUp form and send the details to that particular API's. I want to know the best and if possible easiest way to integrate SignIn/SignUp page into my App. I am not sure of any other cool way to do it ? like hosted library kind of or anything ?