server group api docs are missing some information

This page: https://docs.couchbase.com/server/6.0/rest-api/rest-servergroup-put-membership.html

Two issues:

1- no mention of what the rev id is, means, how it should be used, or where it is looked up. Without more information about rev id, users will not be able to use this endpoint.

2- The example where the json is inline with the curl command does not work. The backslashes cause ns_server to see invalid json. Users that supply a perfectly valid json but with backlashes will always get a failure.