So i am trying to set up a subdomain with a forum for my ruby on rails website which will be hosted on different server. so I have A domain.com hosted on AWS which is built with Ruby On rails then B Community.domain.com hosted on another server. I would like to make community.domain.com a forum, options would be SMF, Mybb, phpbb, or other. Question: Any advice which forum software i could use so that they log in on my website A and still logged in when accessing B or how I would even go about integrating them both?