class Rails::Application::Configuration

config.session_store :my_custom_store
# use ActionDispatch::Session::MyCustomStore as the session store

the +ActionDispatch::Session+ namespace:
If a custom store is specified as a symbol, it will be resolved to

config.session_options # => {key: "_your_app_session"}
config.session_store :cookie_store, key: "_your_app_session"

Additional options will be set as +session_options+:

sessions.
store, or +:disabled+. +:disabled+ tells \Rails not to deal with
are +:cache_store+, +:cookie_store+, +:mem_cache_store+, a custom
Specifies what class to use to store the session. Possible values

def session_store(new_session_store = nil, **options)
  if new_session_store
    @session_store = new_session_store
    @session_options = options || {}
  else
    case @session_store
    when :disabled
      nil
    when Symbol
      ActionDispatch::Session.resolve_store(@session_store)
    else
      @session_store
    end
  end
end