fix(datasource): apply defaults on copy of coerced request

Author: peshence

polytope_server/common/datasource/datasource.py

@@ -18,6 +18,7 @@
 # does it submit to any jurisdiction.
 #
 
+import copy
 import logging
 from abc import ABC
 from importlib import import_module
@@ -66,6 +67,7 @@ def match(ds_config, coerced_ur: Dict[str, Any], user: User) -> str:
         if roles and not user.has_access(roles):
             return f"Skipping datasource {DataSource.repr(ds_config)}: user not authorized."
 
+        coerced_ur = copy.deepcopy(coerced_ur)  # don't want to modify the original request
         # apply defaults
         defaults = ds_config.get("defaults", {})
         if "date" not in defaults: