title: Parse Swift: User relations with a "friends request"
body: <p>I am kind of new to programming and parse, but I am really interested in it. 
  I already know how to create a PFUser and how to set relations between Users, thanks to the tutorial provided on parse.com. The thing is they only have examples for one User following another User. I would prefer sending like a "Friends Request", for example like in instagram if a profile is not open to anybody. 
  How can I code that? What do I need to think of? 
  Example Code is very welcome :P </p>