Switch to custom json

Co-authored-by: David Salvisberg <david.salvisberg@seantis.ch>

Author: Tschuppi81

src/onegov/org/models/ticket.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-import json
+from onegov.custom import json
 from functools import cached_property
 from markupsafe import Markup
 from onegov.chat import Message, MessageCollection