fix: honor tenant validation during plugin imports

tests/test_plugin_compat.py

@@ -0,0 +1,26 @@
+from types import SimpleNamespace
+
+from netbox_export.services.plugin_compat import relation_required_before_save
+
+
+def relation_field(name, related_label):
+    related_model = SimpleNamespace(_meta=SimpleNamespace(label_lower=related_label))
+    return SimpleNamespace(name=name, remote_field=SimpleNamespace(model=related_model))
+
+
+def test_tenant_relation_is_resolved_before_initial_save_when_required():
+    field = relation_field("tenant", "tenancy.tenant")
+
+    assert relation_required_before_save(field, tenant_required=True) is True
+
+
+def test_tenant_relation_can_still_be_deferred_when_policy_is_disabled():
+    field = relation_field("tenant", "tenancy.tenant")
+
+    assert relation_required_before_save(field, tenant_required=False) is False
+
+
+def test_unrelated_relation_is_not_affected_by_tenant_policy():
+    field = relation_field("site", "dcim.site")
+
+    assert relation_required_before_save(field, tenant_required=True) is False