Add documentation for bulk set channel members API (#8876)

* Add documentation for bulk set channel members API

  Add setChannelMembers audit event to the audit log schema and document
  the new PUT /api/v4/channels/{channel_id}/members endpoint in the
  team and channel members admin guide. Introduced in Mattermost v11.7.

* Added example

* Removed examples, which are now in the API docs.

* Update team-channel-members.rst

* Apply suggestion from @wiggin77

---------

Co-authored-by: Eric Sethna <14333569+esethna@users.noreply.github.com>
Co-authored-by: Amy Blais <29708087+amyblais@users.noreply.github.com>

Author: 3 people

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 +153,7 @@ A list of all members in a channel is visible to system admins. Members can be a
 - Member
 - Channel admin
 - System admin
+
+.. note::
+
+   From Mattermost v11.5.2, system admins can set the complete membership of a channel in a single API call. The server computes the diff against the current membership and adds or removes users as needed. See the `API documentation <https://api.mattermost.com/#tag/channels/operation/SetChannelMembers>`__ for details.