chore: broadly detect json family of content-type headers

Author: stainless-app[bot]

src/oxp/_response.py

@@ -233,7 +233,7 @@ def _parse(self, *, to: type[_T] | None = None) -> R | _T:
         # split is required to handle cases where additional information is included
         # in the response, e.g. application/json; charset=utf-8
         content_type, *_ = response.headers.get("content-type", "*").split(";")
-        if content_type != "application/json":
+        if not content_type.endswith("json"):
             if is_basemodel(cast_to):
                 try:
                     data = response.json()