implement stub empty outbox

for #383

activitypub.py

@@ -292,3 +292,20 @@ def follower_collection(domain, collection):
     }
     logger.info(f'Returning {json_dumps(collection, indent=2)}')
     return collection, {'Content-Type': as2.CONTENT_TYPE}
+
+
+@app.get(f'/<regex("{common.DOMAIN_RE}"):domain>/outbox')
+def outbox(domain):
+    url = common.host_url(f"{domain}/outbox")
+    return {
+            '@context': 'https://www.w3.org/ns/activitystreams',
+            'id': url,
+            'summary': f"{domain}'s outbox",
+            'type': 'OrderedCollection',
+            'totalItems': 0,
+            'first': {
+                'type': 'CollectionPage',
+                'partOf': url,
+                'items': [],
+            },
+        }, {'Content-Type': as2.CONTENT_TYPE}

tests/test_activitypub.py

@@ -816,3 +816,20 @@ class ActivityPubTest(testutil.TestCase):
             'next': f'http://localhost/foo.com/following?before={after}',
             'items': [ACTOR],
         }, resp.json)
+
+
+    def test_outbox_empty(self, _, mock_get, __):
+        resp = self.client.get(f'/foo.com/outbox')
+        self.assertEqual(200, resp.status_code)
+        self.assertEqual({
+            '@context': 'https://www.w3.org/ns/activitystreams',
+            'id': 'http://localhost/foo.com/outbox',
+            'summary': "foo.com's outbox",
+            'type': 'OrderedCollection',
+            'totalItems': 0,
+            'first': {
+                'type': 'CollectionPage',
+                'partOf': 'http://localhost/foo.com/outbox',
+                'items': [],
+            },
+        }, resp.json)