Copy default_claims dict to make an id_token

Fix bug where the default_claims dict, defined in the configuration, is
updated on every request.

Author: nsklikas

src/oidcendpoint/id_token.py

@@ -251,7 +251,7 @@ def make(self, req, sess_info, authn_req=None, user_claims=False, **kwargs):
 
         _cinfo = _context.cdb[_client_id]
 
-        default_idtoken_claims = self.kwargs.get("default_claims", None)
+        default_idtoken_claims = dict(self.kwargs.get("default_claims", {}))
         lifetime = self.kwargs.get("lifetime")
 
         userinfo = userinfo_in_id_token_claims(