Fix rds.toJsonObject method only supporting string values

Fixes https://www.notion.so/localstack/Anders-Wasen-GraphQL-Error-for-Non-Nullable-Field-id-in-AppSync-Query-206fc2a2343181e79f95d0fa1dad82e3.

Author: skyrpex

rds/index.js

@@ -20,12 +20,13 @@ export function toJsonObject(inputStr) {
         }
 
         for (const colNo in record) {
-
-          // TODO: what if the column is not a string?
-          const { stringValue } = record[colNo];
           const { label } = columnMetadata[colNo];
 
-          row[label] = stringValue;
+          // We assume that the record is a simple object with a single key-value pair.
+          // For example, `{ longValue: 1 }` or `{ stringValue: "Acme Corp" }`.
+          //
+          // Fixes https://www.notion.so/localstack/Anders-Wasen-GraphQL-Error-for-Non-Nullable-Field-id-in-AppSync-Query-206fc2a2343181e79f95d0fa1dad82e3.
+          row[label] = Object.values(record[colNo])[0];
         }
 
         statement.push(row);