fix availability params (#4905) (#4908)

Author: l-trotta

compiler-rs/clients_schema_to_openapi/src/paths.rs

@@ -74,7 +74,7 @@ pub fn add_endpoint(
             example: None,
             examples: Default::default(),
             explode: None, // Defaults to simple, i.e. comma-separated values for arrays
-            extensions: Default::default(),
+            extensions,
         })
     }