Add documentation for bulk set channel members API

source/administration-guide/comply/embedded-json-audit-log-schema.rst

@@ -256,6 +256,8 @@ Channel Management Events
 +------------------------------------+-------------------------------------------------------------------+
 | ``removeChannelMember``            | Removing members from channels                                    |
 +------------------------------------+-------------------------------------------------------------------+
+| ``setChannelMembers``              | Bulk set (replace) channel memberships                            |
++------------------------------------+-------------------------------------------------------------------+
 | ``restoreChannel``                 | Restoring deleted channels                                        |
 +------------------------------------+-------------------------------------------------------------------+
 | ``updateChannel``                  | Updating channel information                                      |

source/administration-guide/manage/team-channel-members.rst

@@ -153,3 +153,43 @@ A list of all members in a channel is visible to system admins. Members can be a
 - Member
 - Channel admin
 - System admin
+
+Bulk set channel members via the API
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+*Available from Mattermost v11.7*
+
+System admins can set the complete membership of a channel in a single API call using ``PUT /api/v4/channels/{channel_id}/members``. The request body is a JSON array of user IDs representing the desired membership. The server computes the diff against the current membership and adds or removes users as needed, leaving existing members untouched.
+
+Results are streamed back as NDJSON (``application/x-ndjson``), one line per batch. Each line contains ``added``, ``removed``, and ``errors`` arrays for that batch. Query parameters ``batch_size`` (default 100) and ``batch_delay_ms`` (default 500) control the processing rate.
+
+**Example**
+
+Request (using ``batch_size=2`` and ``batch_delay_ms=200``):
+
+.. code-block:: bash
+
+   curl -X PUT \
+     'https://mattermost.example.com/api/v4/channels/channel123/members?batch_size=2&batch_delay_ms=200' \
+     -H 'Authorization: Bearer <token>' \
+     -H 'Content-Type: application/json' \
+     -d '["user_id_1", "user_id_2", "user_id_3", "user_id_4"]'
+
+Streamed NDJSON response (one JSON object per line, one line per batch):
+
+.. code-block:: text
+
+   {"added":[],"removed":["user_id_5","user_id_6"],"errors":[]}
+   {"added":["user_id_3","user_id_4"],"removed":[],"errors":[]}
+   {"added":[],"removed":[],"errors":[{"user_id":"user_id_7","error":"user is not a member of the team"}]}
+
+In this example, ``user_id_1`` and ``user_id_2`` were already members (no-op), ``user_id_5`` and ``user_id_6`` were removed, ``user_id_3`` and ``user_id_4`` were added, and ``user_id_7`` could not be added because the user is not on the team.
+
+Restrictions:
+
+- Requires ``manage_system`` permission (system admin only).
+- DM/GM and group-constrained channels are rejected.
+- Private channels cannot be emptied entirely.
+- Request body is limited to 12 MB.
+
+See the `API documentation <https://api.mattermost.com/#tag/channels/operation/SetChannelMembers>`__ for full details.