root: add group_membership policy

passbook/policies/group_membership/models.py

@@ -0,0 +1,23 @@
+"""user field matcher models"""
+from django.db import models
+from django.utils.translation import gettext as _
+
+from passbook.core.models import Group
+from passbook.policies.models import Policy
+from passbook.policies.types import PolicyRequest, PolicyResult
+
+
+class GroupMembershipPolicy(Policy):
+    """Check that the user is member of the selected group."""
+
+    group = models.ForeignKey(Group, null=True, blank=True, on_delete=models.SET_NULL)
+
+    form = "passbook.policies.group_membership.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")