(core) Customizable stripe plans.

Summary:
- Reading plans from Stripe, and allowing Stripe to define custom plans.
- Storing product features (aka limits) in Stripe, that override those in db.
- Adding hierarchical data in Stripe. All features are defined at Product level but can be overwritten on Price levels.
- New options for Support user to
-- Override product for team site (if he is added as a billing manager)
-- Override subscription and customer id for a team site
-- Attach an "offer", an custom plan configured in stripe that a team site can use
-- Enabling wire transfer for subscription by allowing subscription to be created without a payment method (which is customizable)

Test Plan: Updated and new.

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D4201

app/client/ui2018/loaders.ts

@@ -1,5 +1,5 @@
 import {theme} from 'app/client/ui2018/cssVars';
-import {DomArg, keyframes, styled} from 'grainjs';
+import {DomArg, keyframes, Observable, observable, styled} from 'grainjs';
 
 const rotate360 = keyframes(`
   from { transform: rotate(45deg); }
@@ -42,6 +42,21 @@ export function loadingDots(...args: DomArg<HTMLDivElement>[]) {
   );
 }
 
+export function watchPromise<T extends (...args: any[]) => any>(fun: T): T & {busy: Observable<boolean>} {
+  const loading = observable(false);
+  const result = async (...args: any) => {
+    loading.set(true);
+    try {
+      return await fun(...args);
+    } finally {
+      if (!loading.isDisposed()) {
+        loading.set(false);
+      }
+    }
+  };
+  return Object.assign(result, {busy: loading}) as any;
+}
+
 const cssLoadingDotsContainer = styled('div', `
   --dot-size: 10px;
   display: inline-flex;

app/client/ui2018/modals.ts

@@ -416,8 +416,8 @@ export function confirmModal(
  */
 export function promptModal(
   title: string,
-  onConfirm: (text: string) => Promise<unknown>,
-  btnText: string,
+  onConfirm: (text: string) => Promise<void>,
+  btnText?: string,
   initial?: string,
   placeholder?: string,
   onCancel?: () => void
@@ -429,7 +429,7 @@ export function promptModal(
     const options: ISaveModalOptions = {
       title,
       body: txtInput,
-      saveLabel: btnText,
+      saveLabel: btnText || t('Save'),
       saveFunc: () => {
         // Mark that confirm was invoked.
         confirmed = true;