Added a feature flag to the oauth login feature

issue https://github.com/TryGhost/Team/issues/614

- Makes the feature confiration more similar to other feature flags

ghost/admin/app/controllers/settings/labs.js

@@ -8,11 +8,11 @@ import {
     isRequestEntityTooLargeError,
     isUnsupportedMediaTypeError
 } from 'ghost-admin/services/ajax';
-import {computed, set} from '@ember/object';
 import {isBlank} from '@ember/utils';
 import {isArray as isEmberArray} from '@ember/array';
 import {run} from '@ember/runloop';
 import {inject as service} from '@ember/service';
+import {set} from '@ember/object';
 import {task, timeout} from 'ember-concurrency';
 
 const {Promise} = RSVP;
@@ -72,10 +72,6 @@ export default Controller.extend({
         this.yamlAccept = [...this.yamlMimeType, ...Array.from(this.yamlExtension, extension => '.' + extension)];
     },
 
-    isOAuthEnabled: computed('settings.{oauthClientId,oauthClientSecret}', 'isOAuthConfigurationOpen', function () {
-        return (this.settings.get('oauthClientId') && this.settings.get('oauthClientSecret')) || this.isOAuthConfigurationOpen;
-    }),
-
     actions: {
         onUpload(file) {
             let formData = new FormData();

ghost/admin/app/services/feature.js

@@ -57,6 +57,7 @@ export default Service.extend({
     emailCardSegments: feature('emailCardSegments', {developer: true}),
     savedIndicator: feature('savedIndicator', {developer: true}),
     featureImgDragDrop: feature('featureImgDragDrop', {developer: true}),
+    oauthLogin: feature('oauthLogin', {developer: true}),
 
     _user: null,
 

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

@@ -198,20 +198,11 @@
                             </p>
                         </div>
                         <div class="for-switch">
-                            <label class="switch" for="settings-oauth">
-                                <input
-                                    type="checkbox"
-                                    checked={{this.isOAuthEnabled}}
-                                    id="settings-oauth"
-                                    onclick={{action "toggleIsOAuthEnabled" value="target.checked"}}
-                                    data-test-private-checkbox
-                                >
-                                <span class="input-toggle-component"></span>
-                            </label>
+                            <GhFeatureFlag @flag="oauthLogin" />
                         </div>
                     </div>
                     <div class="gh-expandable-content">
-                        {{#if this.isOAuthEnabled}}
+                        {{#if this.feature.oauthLogin}}
                             <div class="gh-setting-content-extended gh-labs-sso-settings pt2 pb4">
                                 <a href="https://console.developers.google.com/" target="_blank" rel="noopener" class="gh-btn gh-btn-white mb4"><span>{{svg-jar "google-favicon"}}Configure Google OAuth</span></a>
                                 <GhFormGroup @class="no-margin pt2" @errors={{this.settings.errors}} @hasValidated={{this.settings.hasValidated}} @property="password">