Fix cloud webhook body (#20739)

* Bugfix cloud webhooks text response

* address comments

* Fix lint

tests/components/cloud/test_utils.py

@@ -0,0 +1,24 @@
+"""Test aiohttp request helper."""
+from aiohttp import web
+
+from homeassistant.components.cloud import utils
+
+
+def test_serialize_text():
+    """Test serializing a text response."""
+    response = web.Response(status=201, text='Hello')
+    assert utils.aiohttp_serialize_response(response) == {
+        'status': 201,
+        'body': 'Hello',
+        'headers': {'Content-Type': 'text/plain; charset=utf-8'},
+    }
+
+
+def test_serialize_json():
+    """Test serializing a JSON response."""
+    response = web.json_response({"how": "what"})
+    assert utils.aiohttp_serialize_response(response) == {
+        'status': 200,
+        'body': '{"how": "what"}',
+        'headers': {'Content-Type': 'application/json; charset=utf-8'},
+    }