Hid launch-site link on dashboard once wizard is completed

refs https://github.com/TryGhost/Team/issues/460

- use the `user.accessibility` field via the `feature` service to add a `launchComplete` property
  - this is the best place we have currently for UI-specific concerns
- toggle the property to `true` when the "Launch!" button is clicked in the final wizard step
- hide the launch site wizard link on the dashboard if launch has been completed

ghost/admin/app/components/gh-launch-wizard/finalise.hbs

@@ -6,6 +6,12 @@
     </div>
     <div class="gh-launch-wizard-nav-buttons">
         <button type="button" class="gh-btn gh-btn-icon gh-btn-large mr2" {{on "click" @backStep}}><span>{{svg-jar "arrow-left"}}</span></button>
-        <LinkTo @route="dashboard" class="gh-btn gh-btn-black gh-btn-large"><span>Launch your site!</span></LinkTo>
+        <GhTaskButton
+            @task={{this.finaliseTask}}
+            @buttonText="Launch your site!"
+            @runningText="Launching..."
+            @class="gh-btn gh-btn-black gh-btn-large gh-btn-icon"
+            data-test-button="wizard-finish"
+        />
     </div>
 </div>

ghost/admin/app/components/gh-launch-wizard/finalise.js

@@ -0,0 +1,14 @@
+import Component from '@glimmer/component';
+import {inject as service} from '@ember/service';
+import {task} from 'ember-concurrency-decorators';
+
+export default class GhLaunchWizardFinaliseComponent extends Component {
+    @service feature;
+    @service router;
+
+    @task
+    *finaliseTask() {
+        yield this.feature.set('launchComplete', true);
+        this.router.transitionTo('dashboard');
+    }
+}

ghost/admin/app/controllers/dashboard.js

@@ -2,5 +2,6 @@ import Controller from '@ember/controller';
 import {inject as service} from '@ember/service';
 
 export default class DashboardController extends Controller {
+    @service feature;
     @service session;
 }

ghost/admin/app/services/feature.js

@@ -52,6 +52,7 @@ export default Service.extend({
 
     emailAnalytics: feature('emailAnalytics'),
     nightShift: feature('nightShift', {user: true, onChange: '_setAdminTheme'}),
+    launchComplete: feature('launchComplete', {user: true}),
 
     _user: null,
 

ghost/admin/app/templates/dashboard.hbs

@@ -6,7 +6,7 @@
     </GhCanvasHeader>
 
     <section class="view-container gh-main-width">
-        {{#if this.session.user.isOwner}}
+        {{#if (and this.session.user.isOwner (not this.feature.launchComplete))}}
             <LinkTo @route="launch">Launch site - Finish setup</LinkTo>
         {{/if}}
     </section>