*(minor): small refactor

passbook/policies/group/models.py

@@ -0,0 +1,22 @@
+"""passbook group models models"""
+from django.db import models
+from django.utils.translation import gettext as _
+
+from passbook.core.models import Group, Policy
+from passbook.policies.struct import PolicyRequest, PolicyResult
+
+
+class GroupMembershipPolicy(Policy):
+    """Policy to check if the user is member in a certain group"""
+
+    group = models.ForeignKey(Group, on_delete=models.CASCADE)
+
+    form = 'passbook.policies.group.forms.GroupMembershipPolicyForm'
+
+    def passes(self, request: PolicyRequest) -> PolicyResult:
+        return PolicyResult(self.group.user_set.filter(pk=request.user.pk).exists())
+
+    class Meta:
+
+        verbose_name = _('Group Membership Policy')
+        verbose_name_plural = _('Group Membership Policies')