Use feature flag for the MSS Pitch feature

[MAILPOET-2142]

assets/js/src/newsletters/send/congratulate/success.jsx

@@ -4,8 +4,10 @@ import PropTypes from 'prop-types';
 import MSSUserSuccess from './success_for_mss_users.jsx';
 import PitchMss from './success_pitch_mss.jsx';
 
-function Success(props) {
-  if (!window.has_premium_key) {
+import FeaturesContext from '../../../features/context.jsx';
+
+function SuccessContent(props) {
+  if (!window.has_premium_key && props.isSupported('display-mss-pitch')) {
     return (
       <PitchMss
         MSSPitchIllustrationUrl={props.MSSPitchIllustrationUrl}
@@ -25,6 +27,19 @@ function Success(props) {
   );
 }
 
+function Success(props) {
+  return (
+    <FeaturesContext.Consumer>
+      {(FeaturesController) => (
+        <SuccessContent
+          {...props}
+          isSupported={FeaturesController.isSupported}
+        />
+      )}
+    </FeaturesContext.Consumer>
+  );
+}
+
 Success.propTypes = {
   successClicked: PropTypes.func.isRequired,
   illustrationImageUrl: PropTypes.string.isRequired,
@@ -38,5 +53,18 @@ Success.propTypes = {
   mailpoetAccountUrl: PropTypes.string.isRequired,
 };
 
+SuccessContent.propTypes = {
+  successClicked: PropTypes.func.isRequired,
+  illustrationImageUrl: PropTypes.string.isRequired,
+  MSSPitchIllustrationUrl: PropTypes.string.isRequired,
+  newsletter: PropTypes.shape({
+    status: PropTypes.string.isRequired,
+    type: PropTypes.string.isRequired,
+  }).isRequired,
+  isWoocommerceActive: PropTypes.bool.isRequired,
+  subscribersCount: PropTypes.number.isRequired,
+  mailpoetAccountUrl: PropTypes.string.isRequired,
+  isSupported: PropTypes.func.isRequired,
+};
 
 export default Success;

assets/js/src/wizard/steps_numbers.jsx

@@ -1,10 +1,11 @@
+import MailPoet from 'mailpoet';
 
 export const getStepsCount = () => {
   let stepsCount = 3;
   if (window.is_woocommerce_active) {
     stepsCount += 1;
   }
-  if (!window.has_premium_key) {
+  if (!window.has_premium_key && MailPoet.FeaturesController.isSupported('display-mss-pitch')) {
     stepsCount += 1;
   }
   return stepsCount;