systemd owns its package; systemd-networkd configures networkd and claims none

The service manager's package was declared by the networking module, so the
module that is systemd could not own it and had to leave it out. networkd is a
component of systemd: its module configures it. Removing the package resource
from systemd-networkd uninstalls nothing — the host never removes a package
that is not declared absent.

modules/systemd/module.json

@@ -2,7 +2,8 @@
   "module": "systemd",
   "version": "1",
   "capabilities": [
-    "service-manager"
+    "service-manager",
+    "package-manager"
   ],
   "claims": [
     {
@@ -34,5 +35,12 @@
         ]
       }
     ]
-  }
+  },
+  "resources": [
+    {
+      "id": "package",
+      "type": "package",
+      "package": "systemd"
+    }
+  ]
 }