[CORD-3007] Move provider_services and subscriber_service from convenience method to _decl models

Change-Id: I01bf6fe370ddf5abf6e4622ebde345c3e4ba7709
diff --git a/xos/core/models/service.py b/xos/core/models/service.py
index b6bdccf1..75be0f4 100644
--- a/xos/core/models/service.py
+++ b/xos/core/models/service.py
@@ -36,5 +36,21 @@
                 nets.append(net)
         return nets
 
+    @property
+    def provider_services(self):
+        svcs = []
+        service_deps = self.subscribed_dependencies.all()
+        for dep in service_deps:
+            svcs.append(dep.provider_service)
+        return svcs
+
+    @property
+    def subscriber_services(self):
+        svcs = []
+        service_deps = self.provided_dependencies.all()
+        for dep in service_deps:
+            svcs.append(dep.subscriber_service)
+        return svcs
+