Add API endpoints for payment method component

This is part of the paid signup flow

ee/app/controllers/subscriptions_controller.rb

@@ -6,4 +6,20 @@ class SubscriptionsController < ApplicationController
   def new
     return redirect_to dashboard_projects_path unless Feature.enabled?(:paid_signup_flow)
   end
+
+  def payment_form
+    response = client.payment_form_params(params[:id])
+    render json: response[:data]
+  end
+
+  def payment_method
+    response = client.payment_method(params[:id])
+    render json: response[:data]
+  end
+
+  private
+
+  def client
+    Gitlab::SubscriptionPortal::Client
+  end
 end

ee/config/routes/subscription.rb

 # frozen_string_literal: true
 
-resource :subscriptions, only: [:new]
+resource :subscriptions, only: [:new] do
+  get :payment_form
+  get :payment_method
+end

ee/spec/controllers/subscriptions_controller_spec.rb

@@ -3,9 +3,9 @@
 require 'spec_helper'
 
 describe SubscriptionsController do
-  describe 'GET #new' do
-    let_it_be(:user) { create(:user) }
+  let_it_be(:user) { create(:user) }
 
+  describe 'GET #new' do
     subject { get :new, params: { plan_id: 'bronze_id' } }
 
     context 'with unauthorized user' do
@@ -37,4 +37,52 @@ describe SubscriptionsController do
       end
     end
   end
+
+  describe 'GET #payment_form' do
+    subject { get :payment_form, params: { id: 'cc' } }
+
+    context 'with unauthorized user' do
+      it { is_expected.to have_gitlab_http_status 302 }
+      it { is_expected.to redirect_to new_user_session_path }
+    end
+
+    context 'with authorized user' do
+      before do
+        sign_in(user)
+        client_response = { success: true, data: { signature: 'x', token: 'y' } }
+        allow(Gitlab::SubscriptionPortal::Client).to receive(:payment_form_params).with('cc').and_return(client_response)
+      end
+
+      it { is_expected.to have_gitlab_http_status 200 }
+
+      it 'returns the data attribute of the client response in JSON format' do
+        subject
+        expect(response.body).to eq('{"signature":"x","token":"y"}')
+      end
+    end
+  end
+
+  describe 'GET #payment_method' do
+    subject { get :payment_method, params: { id: 'xx' } }
+
+    context 'with unauthorized user' do
+      it { is_expected.to have_gitlab_http_status 302 }
+      it { is_expected.to redirect_to new_user_session_path }
+    end
+
+    context 'with authorized user' do
+      before do
+        sign_in(user)
+        client_response = { success: true, data: { credit_card_type: 'Visa' } }
+        allow(Gitlab::SubscriptionPortal::Client).to receive(:payment_method).with('xx').and_return(client_response)
+      end
+
+      it { is_expected.to have_gitlab_http_status 200 }
+
+      it 'returns the data attribute of the client response in JSON format' do
+        subject
+        expect(response.body).to eq('{"credit_card_type":"Visa"}')
+      end
+    end
+  end
 end