(core) fix invite links and add tests with APP_HOME_URL set

Summary:
Invite links broke when some base domain plumbing changed.
This fix updates them to be aware of the base domain,
and tests the Notifier class with APP_HOME_URL set to
make sure the environment variable has the expected effect.

Test Plan: added test, updated tests

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2630

app/server/lib/FlexServer.ts

@@ -40,7 +40,7 @@ import {addPluginEndpoints, limitToPlugins} from 'app/server/lib/PluginEndpoint'
 import {PluginManager} from 'app/server/lib/PluginManager';
 import {adaptServerUrl, addOrgToPathIfNeeded, addPermit, getScope, optStringParam, RequestWithGristInfo, stringParam,
         TEST_HTTPS_OFFSET, trustOrigin} from 'app/server/lib/requestUtils';
-import {ISendAppPageOptions, makeSendAppPage} from 'app/server/lib/sendAppPage';
+import {ISendAppPageOptions, makeSendAppPage, makeGristConfig} from 'app/server/lib/sendAppPage';
 import {getDatabaseUrl} from 'app/server/lib/serverUtils';
 import {Sessions} from 'app/server/lib/Sessions';
 import * as shutdown from 'app/server/lib/shutdown';
@@ -1031,7 +1031,8 @@ export class FlexServer implements GristServer {
     // and all that is needed is a refactor to pass that info along.  But there is also the
     // case of notification(s) from stripe.  May need to associate a preferred base domain
     // with org/user and persist that?
-    this.notifier = this.create.Notifier(this.dbManager, this.getDefaultHomeUrl());
+    const gristConfig = makeGristConfig(this.getDefaultHomeUrl(), {}, this._defaultBaseDomain);
+    this.notifier = this.create.Notifier(this.dbManager, gristConfig);
   }
 
   public addUsage() {

app/server/lib/ICreate.ts

@@ -1,3 +1,4 @@
+import { GristLoadConfig } from 'app/common/gristUrls';
 import { HomeDBManager } from 'app/gen-server/lib/HomeDBManager';
 import { ActiveDoc } from 'app/server/lib/ActiveDoc';
 import { ScopedSession } from 'app/server/lib/BrowserSession';
@@ -18,7 +19,7 @@ export interface ICreate {
   LoginSession(comm: Comm, sid: string, domain: string, scopeSession: ScopedSession,
                instanceManager: IInstanceManager|null): ILoginSession;
   Billing(dbManager: HomeDBManager): IBilling;
-  Notifier(dbManager: HomeDBManager, homeUrl: string): INotifier;
+  Notifier(dbManager: HomeDBManager, gristConfig: GristLoadConfig): INotifier;
   Shell(): IShell|undefined;
   ExternalStorage(bucket: string, prefix: string): ExternalStorage|undefined;
   ActiveDoc(docManager: DocManager, docName: string): ActiveDoc;

stubs/app/server/lib/create.ts

@@ -19,7 +19,7 @@ export const create: ICreate = {
       addWebhooks(app: any) { /* do nothing */ }
     };
   },
-  Notifier(dbManager: HomeDBManager, homeUrl: string) {
+  Notifier() {
     return {
       get testPending() { return false; }
     };