Add HTTPResponse /api/error/<int:response_code> docs

docs-src/api/Simulating Responses.md

@@ -0,0 +1,19 @@
+Returns the requested HTTP response with a JSON payload containing the response phrase. Valid response codes and phrases are pulled from the [Python `http` library index](https://docs.python.org/3/library/http.html#http.HTTPStatus).
+
+## Endpoint
+```
+GET /api/error/{response_code}
+```
+### Parameters
+Name | Value
+- | -
+`response_code` | The HTTP response code to be returned.
+
+## Example
+```bash
+curl {{production_url}}/api/error/301
+```
+```jsonc
+// Expected Output
+{"message": "Moved Permanently"}
+```