Add Matrix fields to Group and Person

aleksis/apps/matrix/model_extensions.py

+from django.utils.translation import gettext_lazy as _
+
+from jsonstore import CharField
+
+from aleksis.core.models import Group, Person
+
+
+Person.field(matrix_id=CharField(verbose_name=_("Matrix ID")))
+Group.field(matrix_room_id=CharField(verbose_name=_("Matrix room ID")))