Add an admin API to manage ratelimit for a specific user (#9648)

docs/admin_api/user_admin_api.rst

@@ -202,7 +202,7 @@ The following fields are returned in the JSON response body:
 - ``users`` - An array of objects, each containing information about an user.
   User objects contain the following fields:
 
-  - ``name`` - string - Fully-qualified user ID (ex. `@user:server.com`).
+  - ``name`` - string - Fully-qualified user ID (ex. ``@user:server.com``).
   - ``is_guest`` - bool - Status if that user is a guest account.
   - ``admin`` - bool - Status if that user is a server administrator.
   - ``user_type`` - string - Type of the user. Normal users are type ``None``.
@@ -864,3 +864,118 @@ The following parameters should be set in the URL:
 
 - ``user_id`` - The fully qualified MXID: for example, ``@user:server.com``. The user must
   be local.
+
+Override ratelimiting for users
+===============================
+
+This API allows to override or disable ratelimiting for a specific user.
+There are specific APIs to set, get and delete a ratelimit.
+
+Get status of ratelimit
+-----------------------
+
+The API is::
+
+  GET /_synapse/admin/v1/users/<user_id>/override_ratelimit
+
+To use it, you will need to authenticate by providing an ``access_token`` for a
+server admin: see `README.rst <README.rst>`_.
+
+A response body like the following is returned:
+
+.. code:: json
+
+    {
+      "messages_per_second": 0,
+      "burst_count": 0
+    }
+
+**Parameters**
+
+The following parameters should be set in the URL:
+
+- ``user_id`` - The fully qualified MXID: for example, ``@user:server.com``. The user must
+  be local.
+
+**Response**
+
+The following fields are returned in the JSON response body:
+
+- ``messages_per_second`` - integer - The number of actions that can
+  be performed in a second. `0` mean that ratelimiting is disabled for this user.
+- ``burst_count`` - integer - How many actions that can be performed before
+  being limited.
+
+If **no** custom ratelimit is set, an empty JSON dict is returned.
+
+.. code:: json
+
+    {}
+
+Set ratelimit
+-------------
+
+The API is::
+
+  POST /_synapse/admin/v1/users/<user_id>/override_ratelimit
+
+To use it, you will need to authenticate by providing an ``access_token`` for a
+server admin: see `README.rst <README.rst>`_.
+
+A response body like the following is returned:
+
+.. code:: json
+
+    {
+      "messages_per_second": 0,
+      "burst_count": 0
+    }
+
+**Parameters**
+
+The following parameters should be set in the URL:
+
+- ``user_id`` - The fully qualified MXID: for example, ``@user:server.com``. The user must
+  be local.
+
+Body parameters:
+
+- ``messages_per_second`` - positive integer, optional. The number of actions that can
+  be performed in a second. Defaults to ``0``.
+- ``burst_count`` - positive integer, optional. How many actions that can be performed
+  before being limited. Defaults to ``0``.
+
+To disable users' ratelimit set both values to ``0``.
+
+**Response**
+
+The following fields are returned in the JSON response body:
+
+- ``messages_per_second`` - integer - The number of actions that can
+  be performed in a second.
+- ``burst_count`` - integer - How many actions that can be performed before
+  being limited.
+
+Delete ratelimit
+----------------
+
+The API is::
+
+  DELETE /_synapse/admin/v1/users/<user_id>/override_ratelimit
+
+To use it, you will need to authenticate by providing an ``access_token`` for a
+server admin: see `README.rst <README.rst>`_.
+
+An empty JSON dict is returned.
+
+.. code:: json
+
+    {}
+
+**Parameters**
+
+The following parameters should be set in the URL:
+
+- ``user_id`` - The fully qualified MXID: for example, ``@user:server.com``. The user must
+  be local.
+