Https redirect and login cookies on Heroku with Play Framework
Check out the documentation for the setting for default cookie domain.
http://www.playframework.org/documentation/1.2.4/configuration#application.defaultCookieDomain
It explains how you can set a cookie to work across all subdomains.
application.defaultCookieDomain
Enables session/cookie sharing between subdomains. For example, to make cookies valid for all domains ending with ‘.example.com’, e.g. foo.example.com and bar.example.com:
application.defaultCookieDomain=.example.com