Quarantine media by ID or user ID (#6681)

docs/admin_api/media_admin_api.md

@@ -22,19 +22,81 @@ It returns a JSON body like the following:
 }
 ```
 
-# Quarantine media in a room
-
-This API 'quarantines' all the media in a room.
-
-The API is:
-
-```
-POST /_synapse/admin/v1/quarantine_media/<room_id>
-
-{}
-```
+# Quarantine media
 
 Quarantining media means that it is marked as inaccessible by users. It applies
 to any local media, and any locally-cached copies of remote media.
 
 The media file itself (and any thumbnails) is not deleted from the server.
+
+## Quarantining media by ID
+
+This API quarantines a single piece of local or remote media.
+
+Request:
+
+```
+POST /_synapse/admin/v1/media/quarantine/<server_name>/<media_id>
+
+{}
+```
+
+Where `server_name` is in the form of `example.org`, and `media_id` is in the
+form of `abcdefg12345...`.
+
+Response:
+
+```
+{}
+```
+
+## Quarantining media in a room
+
+This API quarantines all local and remote media in a room.
+
+Request:
+
+```
+POST /_synapse/admin/v1/room/<room_id>/media/quarantine
+
+{}
+```
+
+Where `room_id` is in the form of `!roomid12345:example.org`.
+
+Response:
+
+```
+{
+  "num_quarantined": 10  # The number of media items successfully quarantined
+}
+```
+
+Note that there is a legacy endpoint, `POST
+/_synapse/admin/v1/quarantine_media/<room_id >`, that operates the same.
+However, it is deprecated and may be removed in a future release.
+
+## Quarantining all media of a user
+
+This API quarantines all *local* media that a *local* user has uploaded. That is to say, if
+you would like to quarantine media uploaded by a user on a remote homeserver, you should
+instead use one of the other APIs.
+
+Request:
+
+```
+POST /_synapse/admin/v1/user/<user_id>/media/quarantine
+
+{}
+```
+
+Where `user_id` is in the form of `@bob:example.org`.
+
+Response:
+
+```
+{
+  "num_quarantined": 10  # The number of media items successfully quarantined
+}
+```
+