Added the memberAttribution alpha flag

refs https://github.com/TryGhost/Team/issues/1801

This will allow us to develop behind a flag, and switch it to beta
down the line.

ghost/admin/app/services/feature.js

@@ -61,6 +61,7 @@ export default class FeatureService extends Service {
     @feature('beforeAfterCard') beforeAfterCard;
     @feature('newsletterPaywall') newsletterPaywall;
     @feature('freeTrial') freeTrial;
+    @feature('memberAttribution') memberAttribution;
 
     _user = null;
 

ghost/admin/app/templates/settings/labs.hbs

@@ -239,6 +239,19 @@
                         </div>
                     </div>
                 </div>
+                <div class="gh-expandable-block">
+                    <div class="gh-expandable-header">
+                        <div>
+                            <h4 class="gh-expandable-title">Member Attribution</h4>
+                            <p class="gh-expandable-description">
+                               Track which posts & pages are driving Member Subscriptions & Paid Conversions
+                            </p>
+                        </div>
+                        <div class="for-switch">
+                           <GhFeatureFlag @flag="memberAttribution" />
+                        </div>
+                    </div>
+                </div>
             </div>
         </div>
         {{/if}}

ghost/core/core/shared/labs.js

@@ -28,7 +28,8 @@ const ALPHA_FEATURES = [
     'auditLog',
     'urlCache',
     'beforeAfterCard',
-    'freeTrial'
+    'freeTrial',
+    'memberAttribution'
 ];
 
 module.exports.GA_KEYS = [...GA_FEATURES];