(core) add grist.selectedTable.create/update/destroy/upsert to custom widget api

Summary: This makes an equivalent of the /records REST endpoint available within custom widgets. For simple operations, it is compatible with https://github.com/airtable/airtable.js/. About half of the diff is refactoring code from DocApi that implements /records using applyUserActions, to make that code available in the plugin api.

Test Plan: added tests

Reviewers: alexmojaki

Reviewed By: alexmojaki

Differential Revision: https://phab.getgrist.com/D3320

app/plugin/TableOperations.ts

@@ -0,0 +1,44 @@
+import * as Types from 'app/plugin/DocApiTypes';
+
+/**
+ * Offer CRUD-style operations on a table.
+ */
+export interface TableOperations {
+  // Create a record or records.
+  create(records: Types.NewRecord, options?: OpOptions): Promise<Types.MinimalRecord>;
+  create(records: Types.NewRecord[], options?: OpOptions): Promise<Types.MinimalRecord[]>;
+
+  // Update a record or records.
+  update(records: Types.Record|Types.Record[], options?: OpOptions): Promise<void>;
+
+  // Delete a record or records.
+  destroy(recordId: Types.RecordId): Promise<Types.RecordId>;
+  destroy(recordIds: Types.RecordId[]): Promise<Types.RecordId[]>;
+
+  // Add or update a record or records.
+  upsert(records: Types.AddOrUpdateRecord|Types.AddOrUpdateRecord[],
+         options?: UpsertOptions): Promise<void>;
+
+  // TODO: offer a way to query the table.
+  // select(): Records;
+}
+
+/**
+ * General options for table operations.
+ * By default, string field values will be parsed based on the column type.
+ * This can be disabled.
+ */
+export interface OpOptions {
+  parseStrings?: boolean;
+}
+
+/**
+ * Extra options for upserts. By default, add and update are true,
+ * onMany is first, and allowEmptyRequire is false.
+ */
+export interface UpsertOptions extends OpOptions {
+  add?: boolean;      // permit inserting a record
+  update?: boolean;   // permit updating a record
+  onMany?: 'none' | 'first' | 'all';  // whether to update none, one, or all matching records
+  allowEmptyRequire?: boolean; // allow "wildcard" operation
+}