(core) Implement UI for trigger formulas.

Summary:
- Implement UI with "Apply to new records" and "Apply on record changes"
  checkboxes, and options for selecting which changes to recalculate on.
- For consistency, always represent empty RefList as None
- Fix up generated SchemaTypes to remember that values are encoded.

Included test cases for the main planned use cases:
- Auto-filled UUID column
- Data cleaning
- NOW() formula for record's last-updated timestamp.
- Updates that depend on other columns.

Test Plan: Added a browser test.

Reviewers: jarek

Reviewed By: jarek

Subscribers: paulfitz

Differential Revision: https://phab.getgrist.com/D2885

app/client/components/GridView.js

@@ -529,7 +529,7 @@ GridView.prototype._convertFormulasToData = function(selection) {
   // prevented by ACL rules).
   const fields = selection.fields.filter(f => f.column.peek().isFormula.peek());
   if (!fields.length) { return null; }
-  return this.gristDoc.convertFormulasToData(fields.map(f => f.colRef.peek()));
+  return this.gristDoc.convertIsFormula(fields.map(f => f.colRef.peek()), {toFormula: false});
 };
 
 GridView.prototype.selectAll = function() {

app/client/components/GristDoc.ts

@@ -42,6 +42,7 @@ import {DisposableWithEvents} from 'app/common/DisposableWithEvents';
 import {isSchemaAction} from 'app/common/DocActions';
 import {OpenLocalDocResult} from 'app/common/DocListAPI';
 import {HashLink, IDocPage} from 'app/common/gristUrls';
+import {RecalcWhen} from 'app/common/gristTypes';
 import {encodeQueryParams, waitObs} from 'app/common/gutil';
 import {StringUnion} from 'app/common/StringUnion';
 import {TableData} from 'app/common/TableData';
@@ -572,16 +573,20 @@ export class GristDoc extends DisposableWithEvents {
       ['BulkUpdateRecord', colRefs, {
         isFormula: colRefs.map(f => true),
         formula: colRefs.map(f => ''),
+        // Set recalc settings to defaults when emptying a column.
+        recalcWhen: colRefs.map(f => RecalcWhen.DEFAULT),
+        recalcDeps: colRefs.map(f => null),
       }]
     );
   }
 
   // Convert the given columns to data, saving the calculated values and unsetting the formulas.
-  public async convertFormulasToData(colRefs: number[]): Promise<void> {
+  public async convertIsFormula(colRefs: number[], opts: {toFormula: boolean, noRecalc?: boolean}): Promise<void> {
     return this.docModel.columns.sendTableAction(
       ['BulkUpdateRecord', colRefs, {
-        isFormula: colRefs.map(f => false),
-        formula: colRefs.map(f => ''),
+        isFormula: colRefs.map(f => opts.toFormula),
+        recalcWhen: colRefs.map(f => opts.noRecalc ? RecalcWhen.NEVER : RecalcWhen.DEFAULT),
+        recalcDeps: colRefs.map(f => null),
       }]
     );
   }