Simplify the authentication concern

Explaining method was left explaining nothing and the conditional guard
wasnt necessary either (since Current.session should already be nil
anyway by this point!)

Author: dhh

railties/lib/rails/generators/rails/authentication/templates/controllers/concerns/authentication.rb

@@ -23,9 +23,7 @@ def require_authentication
 
 
     def resume_session
-      if session = find_session_by_cookie
-        set_current_session session
-      end
+      Current.session = find_session_by_cookie
     end
 
     def find_session_by_cookie
@@ -45,15 +43,11 @@ def after_authentication_url
 
     def start_new_session_for(user)
       user.sessions.create!(user_agent: request.user_agent, ip_address: request.remote_ip).tap do |session|
-        set_current_session session
+        Current.session = session
         cookies.signed.permanent[:session_id] = { value: session.id, httponly: true, same_site: :lax }
       end
     end
 
-    def set_current_session(session)
-      Current.session = session
-    end
-
     def terminate_session
       Current.session.destroy
       cookies.delete(:session_id)