Prepare NPM references and mutation API

tests/test_npm_adapter.py

@@ -7,6 +7,7 @@ from dns_sync.adapters import (
     PROXY_HOSTS,
     Capability,
     CapabilityOperation,
+    ObjectReference,
 )
 from dns_sync.config import AppConfig
 from dns_sync.registry import load_adapter
@@ -110,6 +111,38 @@ class NpmAdapterTests(unittest.TestCase):
             discovered[0].payload,
         )
 
+        self.assertEqual(
+            discovered[0].references,
+            (
+                ObjectReference(
+                    relation="certificate",
+                    object_type=CERTIFICATES,
+                    local_key="67",
+                ),
+            ),
+        )
+
+    def test_proxy_host_without_certificate_has_no_reference(self):
+        client = Mock()
+        client.proxy_hosts.return_value = [
+            {
+                "id": 13,
+                "domain_names": ["plain.example.com"],
+                "forward_scheme": "http",
+                "forward_host": "192.168.1.20",
+                "forward_port": 8080,
+                "certificate_id": 0,
+                "enabled": 1,
+            }
+        ]
+        adapter = self.adapter(client)
+
+        discovered = adapter.discover(PROXY_HOSTS)
+
+        self.assertEqual(len(discovered), 1)
+        self.assertEqual(discovered[0].references, ())
+
+
     def test_certificate_discovery_excludes_secret_material(self):
         client = Mock()
         client.certificates.return_value = [