Add GeoNodeGroupLink model

app/models/geo_node.rb

@@ -5,6 +5,9 @@ class GeoNode < ActiveRecord::Base
   belongs_to :oauth_application, class_name: 'Doorkeeper::Application', dependent: :destroy # rubocop: disable Cop/ActiveRecordDependent
   belongs_to :system_hook, dependent: :destroy # rubocop: disable Cop/ActiveRecordDependent
 
+  has_many :geo_node_group_links
+  has_many :groups, through: :geo_node_group_links
+
   default_values schema: lambda { Gitlab.config.gitlab.protocol },
                  host: lambda { Gitlab.config.gitlab.host },
                  port: lambda { Gitlab.config.gitlab.port },

app/models/geo_node_group_link.rb

+class GeoNodeGroupLink < ActiveRecord::Base
+  belongs_to :geo_node
+  belongs_to :group
+
+  validates :geo_node_id, :group_id, presence: true
+  validates :group_id, uniqueness: { scope: [:geo_node_id] }
+end

spec/factories/geo_node_group_links.rb

+FactoryGirl.define do
+  factory :geo_node_group_link do
+    geo_node
+    group
+  end
+end

spec/models/geo_node_group_link_spec.rb

+require 'spec_helper'
+
+describe GeoNodeGroupLink, models: true do
+  describe 'relationships' do
+    it { is_expected.to belong_to(:geo_node) }
+    it { is_expected.to belong_to(:group) }
+  end
+
+  describe 'validations' do
+    let!(:geo_node_group_link) { create(:geo_node_group_link) }
+
+    it { is_expected.to validate_presence_of(:geo_node_id) }
+    it { is_expected.to validate_presence_of(:group_id) }
+    it { is_expected.to validate_uniqueness_of(:group_id).scoped_to(:geo_node_id) }
+  end
+end

spec/models/geo_node_spec.rb

@@ -14,6 +14,9 @@ describe GeoNode, type: :model do
   context 'associations' do
     it { is_expected.to belong_to(:geo_node_key).dependent(:destroy) }
     it { is_expected.to belong_to(:oauth_application).dependent(:destroy) }
+
+    it { is_expected.to have_many(:geo_node_group_links) }
+    it { is_expected.to have_many(:groups).through(:geo_node_group_links) }
   end
 
   context 'default values' do