JETS-382: Add custom data bad request case

Author: JQuinnie

source/api_documentation/signal_api/index.rst

@@ -235,7 +235,7 @@ For example, if a **transaction_id** or **call_start_time** are not passed in th
 
 If there are multiple issues with the request, we will do our best to package all of the issues together in one response message.
 
-**Example Bad Request**
+**Example Bad Signal Request**
 
 .. code-block:: json
 
@@ -279,6 +279,31 @@ If there are multiple issues with the request, we will do our best to package al
     }
   }
 
+**Example Bad Custom Data Request**
+
+.. code-block:: json
+
+  {
+    "search": {
+      "transaction_id": "0000000-0000000A"
+    },
+    "custom_data": {
+      "agent": "James Bond"
+    },
+    "oauth_token": "<YOUR OAUTH TOKEN>"
+  }
+
+**Response (403 Forbidden):**
+
+.. code-block:: json
+
+  {
+    "errors": {
+      "class": "InvalidInput",
+      "invalid_data": "'custom_data' must be an array of hashes"
+    }
+  }
+
 -----
 
 **Record Invalid Error**