Use relative time for recent dates in case summaries

Comes with an option to toggle on/off and to set the "recent" threshold.

backend/src/plugins/Cases/CasesPlugin.ts

@@ -17,6 +17,8 @@ const defaultOptions = {
   config: {
     log_automatic_actions: true,
     case_log_channel: null,
+    show_relative_times: true,
+    relative_time_cutoff: "7d",
   },
 };