add api.runAsyncOnBackendWithManualTransactionHandling() variant and add toast warnings about improper usage.

src/routes/api/script.js

@@ -4,12 +4,16 @@ const scriptService = require('../../services/script');
 const attributeService = require('../../services/attributes');
 const becca = require('../../becca/becca');
 const syncService = require('../../services/sync');
+const sql = require('../../services/sql');
 
+// The async/await here is very confusing, because the body.script may, but may not be async. If it is async, then we
+// need to await it and make the complete response including metadata available in a Promise, so that the route detects
+// this and does result.then().
 async function exec(req) {
     try {
         const {body} = req;
 
-        const result = await scriptService.executeScript(
+        const execute = body => scriptService.executeScript(
             body.script,
             body.params,
             body.startNoteId,
@@ -18,6 +22,10 @@ async function exec(req) {
             body.originEntityId
         );
 
+        const result = body.transactional
+            ? sql.transactional(() => execute(body))
+            : await execute(body);
+
         return {
             success: true,
             executionResult: result,