[python] fix content_type deserialize (#19317)

* [Python] fix: #19285

* [python] update sample

* [python] add test

* [python] remove test

samples/client/echo_api/python/openapi_client/api_client.py

@@ -405,12 +405,12 @@ class ApiClient:
                 data = json.loads(response_text)
             except ValueError:
                 data = response_text
-        elif content_type.startswith("application/json"):
+        elif re.match(r'^application/(json|[\w!#$&.+-^_]+\+json)\s*(;|$)', content_type, re.IGNORECASE):
             if response_text == "":
                 data = ""
             else:
                 data = json.loads(response_text)
-        elif content_type.startswith("text/plain"):
+        elif re.match(r'^text/plain\s*(;|$)', content_type, re.IGNORECASE):
             data = response_text
         else:
             raise ApiException(