Add service to generate default board lists

app/services/boards/lists/generate_service.rb

+module Boards
+  module Lists
+    class GenerateService < Boards::BaseService
+      def execute
+        return false unless board.lists.label.empty?
+
+        List.transaction do
+          label_params.each { |params| create_list(params) }
+        end
+
+        true
+      end
+
+      private
+
+      def create_list(params)
+        label = find_or_create_label(params)
+        CreateService.new(project, user, label_id: label.id).execute
+      end
+
+      def find_or_create_label(params)
+        project.labels.create_with(color: params[:color])
+                      .find_or_create_by(name: params[:name])
+      end
+
+      def label_params
+        [
+          { name: 'Development', color: '#5CB85C' },
+          { name: 'Testing',     color: '#F0AD4E' },
+          { name: 'Production',  color: '#FF5F00' },
+          { name: 'Ready',       color: '#FF0000' }
+        ]
+      end
+    end
+  end
+end

spec/services/boards/lists/generate_service_spec.rb

+require 'spec_helper'
+
+describe Boards::Lists::GenerateService, services: true do
+  describe '#execute' do
+    let(:project) { create(:project_with_board) }
+    let(:board)   { project.board }
+    let(:user)    { create(:user) }
+
+    subject(:service) { described_class.new(project, user) }
+
+    context 'when board lists is empty' do
+      it 'creates the default lists' do
+        expect { service.execute }.to change(board.lists, :count).by(4)
+      end
+    end
+
+    context 'when board lists is not empty' do
+      it 'does not creates the default lists' do
+        create(:list, board: board)
+
+        expect { service.execute }.not_to change(board.lists, :count)
+      end
+    end
+
+    context 'when project labels does not contains any list label' do
+      it 'creates labels' do
+        expect { service.execute }.to change(project.labels, :count).by(4)
+      end
+    end
+
+    context 'when project labels contains some of list label' do
+      it 'creates the missing labels' do
+        create(:label, project: project, name: 'Development')
+        create(:label, project: project, name: 'Ready')
+
+        expect { service.execute }.to change(project.labels, :count).by(2)
+      end
+    end
+  end
+end