Include models in admin interface

This function shouldn't be used to change or delete data, but it's a useful tool for administrators to check how imports were done.

aleksis/apps/chronos/util/format.py

+from django.utils.formats import date_format
+
+
+def format_m2m(f, attr: str = "short_name"):
+    return ", ".join([getattr(x, attr) for x in f.all()])
+
+
+def format_date_period(date, period):
+    return "{}, {}.".format(date_format(date), period.period)