added group model

+class Group < ApplicationRecord
+  belongs_to :user, -> { with_deleted }, inverse_of: :groups
+  belongs_to :pool, -> { with_deleted }, inverse_of: :groups
+end

@@ -16,6 +16,8 @@ class Pool < ApplicationRecord
   validates :name, :editable_until, presence: true
 
   has_many :matches, dependent: :destroy, inverse_of: :pool
+  has_many :groups, inverse_of: :pool
+  has_many :users, through: :groups, inverse_of: :pools
 
   scope :active, -> { where(active: true) }
   accepts_nested_attributes_for :matches, reject_if: :all_blank,

@@ -27,6 +27,8 @@ class User < ApplicationRecord
   before_save :encrypt_password
 
   has_many :bets, inverse_of: :user
+  has_many :groups, inverse_of: :user
+  has_many :pools, through: :groups, inverse_of: :users
 
   has_and_belongs_to_many :roles, inverse_of: :users,
                         class_name: 'HeimdallEngine::Role',

+class CreateGroups < ActiveRecord::Migration[5.0]
+  def change
+    create_table :groups do |t|
+      t.integer :user_id, index: true
+      t.integer :pool_id, index: true
+      t.timestamps
+    end
+  end
+end

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180608221342) do
+ActiveRecord::Schema.define(version: 20180611152223) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -24,6 +24,15 @@ ActiveRecord::Schema.define(version: 20180608221342) do
     t.integer "points"
   end
 
+  create_table "groups", force: :cascade do |t|
+    t.integer  "user_id"
+    t.integer  "pool_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["pool_id"], name: "index_groups_on_pool_id", using: :btree
+    t.index ["user_id"], name: "index_groups_on_user_id", using: :btree
+  end
+
   create_table "heimdall_engine_role_abilities", force: :cascade do |t|
     t.integer  "role_id"
     t.string   "key"

+# Read about fixtures at http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+
+one:
+  user_id: 1
+  pool_id: 1
+
+two:
+  user_id: 1
+  pool_id: 1

+require 'test_helper'
+
+class GroupTest < ActiveSupport::TestCase
+  # test "the truth" do
+  #   assert true
+  # end
+end