(core) Tweak navbar, breadcrumbs, and sign-in buttons

Summary:
The changes are intended to smooth over some sharp edges when a signed-out user
is using Grist (particularly while on the templates site).

Test Plan: Browser tests.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3957

app/gen-server/ApiServer.ts

@@ -14,17 +14,13 @@ import {RequestWithOrg} from 'app/server/lib/extractOrg';
 import log from 'app/server/lib/log';
 import {addPermit, clearSessionCacheIfNeeded, getDocScope, getScope, integerParam,
         isParameterOn, optStringParam, sendOkReply, sendReply, stringParam} from 'app/server/lib/requestUtils';
+import {getTemplateOrg} from 'app/server/lib/sendAppPage';
 import {IWidgetRepository} from 'app/server/lib/WidgetRepository';
 
 import {User} from './entity/User';
 import {HomeDBManager, QueryResult, Scope} from './lib/HomeDBManager';
 import {getCookieDomain} from 'app/server/lib/gristSessions';
 
-// Special public organization that contains examples and templates.
-export const TEMPLATES_ORG_DOMAIN = process.env.GRIST_ID_PREFIX ?
-  `templates-${process.env.GRIST_ID_PREFIX}` :
-  'templates';
-
 // exposed for testing purposes
 export const Deps = {
   apiKeyGenerator: () => crypto.randomBytes(20).toString('hex')
@@ -247,10 +243,15 @@ export class ApiServer {
     // GET /api/templates/
     // Get all templates (or only featured templates if `onlyFeatured` is set).
     this._app.get('/api/templates/', expressWrap(async (req, res) => {
+      const templateOrg = getTemplateOrg();
+      if (!templateOrg) {
+        throw new ApiError('Template org is not configured', 500);
+      }
+
       const onlyFeatured = isParameterOn(req.query.onlyFeatured);
       const query = await this._dbManager.getOrgWorkspaces(
         {...getScope(req), showOnlyPinned: onlyFeatured},
-        TEMPLATES_ORG_DOMAIN
+        templateOrg
       );
       return sendReply(req, res, query);
     }));