add documentation

doc/utils/lambda.md

@@ -0,0 +1,36 @@
+# Lambda
+
+## Functions
+
+### `invokeLambdaFunction(input:{functionName: string; payload: object})`
+
+Invoke a Lambda function.
+
+Parameters:
+- `functionName`: the Lambda function name
+- `payload`: the payload/event to send to the Lambda function
+
+Note: `invokeLambdaFunction` automatically parses the response from the Lambda function and returns either a `string` or an `object` (JSON object) depending on the returned value of the Lambda function: if the Lambda function returns a string, the result will be of type string; if it returns an object, the result will be of type object.
+
+example:
+```typescript
+const result1 = await invokeLambdaFunction({
+      functionName: 'sum',
+      payload: {
+        a: 1,
+        b: 2,
+      },
+    });
+
+console.log(result1) // 3
+
+const result2 = await invokeLambdaFunction({
+      functionName: 'sum-json',
+      payload: {
+        a: 1,
+        b: 2,
+      },
+    });
+
+console.log(result2) // { "result" : 3 }
+```