add application service

app/services/applications/create_service.rb

+module Applications
+  class CreateService < ::Emails::BaseService
+    #prepend ::EE::Applications::CreateService
+
+    def initialize(current_user, params)
+      @current_user = current_user
+      @params = params
+    end
+
+    def execute
+      Doorkeeper::Application.create(@params)
+    end
+  end
+end

spec/services/applications/create_service_spec.rb

+require 'spec_helper'
+
+describe ::Applications::CreateService do
+  let(:user) { create(:user) }
+  let(:params) { attributes_for(:application) }
+
+  subject { described_class.new(user, params) }
+
+  it 'creates an application' do
+    expect { subject.execute }.to change { Doorkeeper::Application.count }.by(1)
+  end
+end