added missing value_type to Bytea column

Needed for Pydantic serialisation

Author: dantownsend

piccolo/columns/column_types.py

@@ -1243,6 +1243,8 @@ class Token(Table):
 
     """
 
+    value_type = bytes
+
     @property
     def column_type(self):
         engine_type = self._meta.table._meta.db.engine_type