AdminPanel: add the toggle for enterprise

Final ingredient. This surfaces the work in creating the backend
config API, the frontend model, the grainjs observable, and the
grainjs DOM and CSS components.

app/client/ui/AdminPanel.ts

@@ -9,6 +9,7 @@ import {AppHeader} from 'app/client/ui/AppHeader';
 import {leftPanelBasic} from 'app/client/ui/LeftPanelCommon';
 import {pagePanels} from 'app/client/ui/PagePanels';
 import {SupportGristPage} from 'app/client/ui/SupportGristPage';
+import {ToggleEnterpriseWidget} from 'app/client/ui/ToggleEnterpriseWidget';
 import {createTopBarHome} from 'app/client/ui/TopBar';
 import {cssBreadcrumbs, separator} from 'app/client/ui2018/breadcrumbs';
 import {basicButton} from 'app/client/ui2018/buttons';
@@ -25,7 +26,6 @@ import {Computed, Disposable, dom, IDisposable,
         IDisposableOwner, MultiHolder, Observable, styled} from 'grainjs';
 import {AdminSection, AdminSectionItem, HidableToggle} from 'app/client/ui/AdminPanelCss';
 
-
 const t = makeT('AdminPanel');
 
 // Translated "Admin Panel" name, made available to other modules.
@@ -35,6 +35,7 @@ export function getAdminPanelName() {
 
 export class AdminPanel extends Disposable {
   private _supportGrist = SupportGristPage.create(this, this._appModel);
+  private _toggleEnterprise = ToggleEnterpriseWidget.create(this);
   private readonly _installAPI: InstallAPI = new InstallAPIImpl(getHomeUrl());
   private _checks: AdminChecks;
 
@@ -161,6 +162,13 @@ Please log in as an administrator.`)),
           description: t('Current version of Grist'),
           value: cssValueLabel(`Version ${version.version}`),
         }),
+        dom.create(AdminSectionItem, {
+          id: 'enterprise',
+          name: t('Enterprise'),
+          description: t('Enable Grist Enterprise'),
+          value: dom.create(HidableToggle, this._toggleEnterprise.getEnterpriseToggleObservable()),
+          expandedContent: this._toggleEnterprise.buildEnterpriseSection(),
+        }),
         this._buildUpdates(owner),
       ]),
       dom.create(AdminSection, t('Self Checks'), [