Add system console switch for enabling link previews (#5663)

webapp/components/admin_console/admin_sidebar.jsx

@@ -689,6 +689,16 @@ export default class AdminSidebar extends React.Component {
 
                                     }
                                 />
+                                <AdminSidebarSection
+                                    name='link_previews'
+                                    title={
+                                        <FormattedMessage
+                                            id='admin.sidebar.linkPreviews'
+                                            defaultMessage='Link Previews'
+                                        />
+
+                                    }
+                                />
                                 <AdminSidebarSection
                                     name='legal_and_support'
                                     title={

webapp/components/admin_console/link_previews_settings.jsx

@@ -0,0 +1,66 @@
+// Copyright (c) 2017 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+import React from 'react';
+
+import AdminSettings from './admin_settings.jsx';
+import BooleanSetting from './boolean_setting.jsx';
+import {FormattedMessage} from 'react-intl';
+import SettingsGroup from './settings_group.jsx';
+
+export default class LinkPreviewsSettings extends AdminSettings {
+    constructor(props) {
+        super(props);
+
+        this.getConfigFromState = this.getConfigFromState.bind(this);
+
+        this.renderSettings = this.renderSettings.bind(this);
+    }
+
+    getConfigFromState(config) {
+        config.ServiceSettings.EnableLinkPreviews = this.state.enableLinkPreviews;
+
+        return config;
+    }
+
+    getStateFromConfig(config) {
+        return {
+            enableLinkPreviews: config.ServiceSettings.EnableLinkPreviews
+        };
+    }
+
+    renderTitle() {
+        return (
+            <h3>
+                <FormattedMessage
+                    id='admin.customization.linkPreviews'
+                    defaultMessage='Link Previews'
+                />
+            </h3>
+        );
+    }
+
+    renderSettings() {
+        return (
+            <SettingsGroup>
+                <BooleanSetting
+                    id='enableLinkPreviews'
+                    label={
+                        <FormattedMessage
+                            id='admin.customization.enableLinkPreviewsTitle'
+                            defaultMessage='Enable Link Previews:'
+                        />
+                    }
+                    helpText={
+                        <FormattedMessage
+                            id='admin.customization.enableLinkPreviewsDesc'
+                            defaultMessage='Enable users to display a preview of website content below the message, if available. When true, website previews can be enabled from Account Settings > Advanced > Preview pre-release features.'
+                        />
+                    }
+                    value={this.state.enableLinkPreviews}
+                    onChange={this.handleChange}
+                />
+            </SettingsGroup>
+        );
+    }
+}