(core) set up a trialing list and a call scheduled flag for Grist SaaS

Summary:
This adds support for the automation described in
https://grist.quip.com/rt3tAoEH4kuy/Automate-Sprouts-outreach-email

Test Plan: added tests; will need manual testing and iterative integration work

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D3804

app/client/ui/AppUI.ts

@@ -53,7 +53,7 @@ export function createAppUI(topAppModel: TopAppModel, appObj: App): IDisposable
 }
 
 function createMainPage(appModel: AppModel, appObj: App) {
-  if (!appModel.currentOrg && appModel.pageType.get() !== 'welcome') {
+  if (!appModel.currentOrg && appModel.needsOrg.get()) {
     const err = appModel.orgError;
     if (err && err.status === 404) {
       return createNotFoundPage(appModel);