fix: Permission DoesNotExist when accessing BaseInvoice history

See the issue for details.

Closes #317 .

cotisations/migrations/0003_auto_20210124_1105.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.29 on 2021-01-24 10:05
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('cotisations', '0002_foreign_keys'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='baseinvoice',
+            options={'permissions': (('view_baseinvoice', 'Can view an base invoice object'),)},
+        ),
+    ]

cotisations/models.py

@@ -60,6 +60,12 @@ from cotisations.validators import check_no_balance
 class BaseInvoice(RevMixin, AclMixin, FieldPermissionModelMixin, models.Model):
     date = models.DateTimeField(auto_now_add=True, verbose_name=_("date"))
 
+    class Meta:
+        abstract = False
+        permissions = (
+            ("view_baseinvoice", _("Can view an base invoice object")),
+        )
+
     # TODO : change prix to price
     def prix(self):
         """