Add /user/{user_id}/shared_rooms/ api (#7785)

* Add shared_rooms api

* Add changelog

* Add .

* Wrap response in {"rooms": }

* linting

* Add unstable_features key

* Remove options from isort that aren't part of 5.x

`-y` and `-rc` are now default behaviour and no longer exist.

`dont-skip` is no longer required

https://timothycrosley.github.io/isort/CHANGELOG/#500-penny-july-4-2020

* Update imports to make isort happy

* Add changelog

* Update tox.ini file with correct invocation

* fix linting again for isort

* Vendor prefix unstable API

* Fix to match spec

* import Codes

* import Codes

* Use FORBIDDEN

* Update changelog.d/7785.feature

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

* Implement get_shared_rooms_for_users

* a comma

* trailing whitespace

* Handle the easy feedback

* Switch to using runInteraction

* Add tests

* Feedback

* Seperate unstable endpoint from v2

* Add upgrade node

* a line

* Fix style by adding a blank line at EOF.

* Update synapse/storage/databases/main/user_directory.py

Co-authored-by: Tulir Asokan <tulir@maunium.net>

* Update synapse/storage/databases/main/user_directory.py

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

* Update UPGRADE.rst

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

* Fix UPGRADE/CHANGELOG unstable paths

unstable unstable unstable

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Co-authored-by: Tulir Asokan <tulir@maunium.net>

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>
Co-authored-by: Tulir Asokan <tulir@maunium.net>

synapse/rest/client/v2_alpha/shared_rooms.py

@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 Half-Shot
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+
+from synapse.api.errors import Codes, SynapseError
+from synapse.http.servlet import RestServlet
+from synapse.types import UserID
+
+from ._base import client_patterns
+
+logger = logging.getLogger(__name__)
+
+
+class UserSharedRoomsServlet(RestServlet):
+    """
+    GET /uk.half-shot.msc2666/user/shared_rooms/{user_id} HTTP/1.1
+    """
+
+    PATTERNS = client_patterns(
+        "/uk.half-shot.msc2666/user/shared_rooms/(?P<user_id>[^/]*)",
+        releases=(),  # This is an unstable feature
+    )
+
+    def __init__(self, hs):
+        super(UserSharedRoomsServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+        self.user_directory_active = hs.config.update_user_directory
+
+    async def on_GET(self, request, user_id):
+
+        if not self.user_directory_active:
+            raise SynapseError(
+                code=400,
+                msg="The user directory is disabled on this server. Cannot determine shared rooms.",
+                errcode=Codes.FORBIDDEN,
+            )
+
+        UserID.from_string(user_id)
+
+        requester = await self.auth.get_user_by_req(request)
+        if user_id == requester.user.to_string():
+            raise SynapseError(
+                code=400,
+                msg="You cannot request a list of shared rooms with yourself",
+                errcode=Codes.FORBIDDEN,
+            )
+        rooms = await self.store.get_shared_rooms_for_users(
+            requester.user.to_string(), user_id
+        )
+
+        return 200, {"joined": list(rooms)}
+
+
+def register_servlets(hs, http_server):
+    UserSharedRoomsServlet(hs).register(http_server)