Fix different cases of response header names (#415)

packages/atproto_client/request.py

@@ -27,17 +27,12 @@ class Response:
 
 
 def _convert_headers_to_dict(headers: httpx.Headers) -> t.Dict[str, str]:
-    headers_dict: t.Dict[str, str] = {}
+    """Convert custom case-insensitive multi-dict of HTTPX to pure dict with lowercased keys.
 
-    for key, value in headers.raw:
-        str_key = key.decode(headers.encoding)
-        str_value = value.decode(headers.encoding)
-        if str_key in headers_dict:
-            headers_dict[str_key] += f', {str_value}'
-        else:
-            headers_dict[str_key] = str_value
-
-    return headers_dict
+    Note:
+        Concatenate headers into a single comma separated value when a key occurs multiple times.
+    """
+    return dict(headers.items())
 
 
 def _parse_response(response: httpx.Response) -> Response: