Validate message file upload limit

discord/http.py

@@ -173,6 +173,9 @@ def handle_message_parameters(
     if attachments is not MISSING and files is not MISSING:
         raise TypeError('Cannot mix attachments and files keyword arguments.')
 
+    if files is not MISSING and len(files) > 10:
+        raise ValueError('files has a maximum of 10 elements.')
+
     payload = {}
     if embeds is not MISSING:
         if len(embeds) > 10:

discord/webhook/async_.py

@@ -571,6 +571,9 @@ def interaction_message_response_params(
     if attachments is not MISSING and files is not MISSING:
         raise TypeError('Cannot mix attachments and files keyword arguments.')
 
+    if files is not MISSING and len(files) > 10:
+        raise ValueError('files has a maximum of 10 elements.')
+
     data: Optional[Dict[str, Any]] = {
         'tts': tts,
     }