[admin] allow to filter out users with no memberships

Author: markets

app/admin/user.rb

@@ -16,6 +16,9 @@
     redirect_to action: :index
   end
 
+  scope :all
+  scope :without_memberships
+
   index do
     selectable_column
     column do |user|

app/models/user.rb

@@ -38,6 +38,7 @@ class User < ApplicationRecord
   accepts_nested_attributes_for :members, allow_destroy: true
 
   default_scope { order("users.id ASC") }
+  scope :without_memberships, -> { where.missing(:members) }
   scope :actives, -> { joins(:members).where(members: { active: true }) }
   scope :online_active, -> { where("sign_in_count > 0") }
   scope :notifications, -> { where(notifications: true) }