Document the winning_rev_only document_changed webook option

In SG 2.8.1 and later we added an opt-in config option to only fire the document_changed webhook event handler when the document being changed is the winning revision.

This avoids webhook spam when resolving conflicts by removing old non-winning revisions of documents.

Note: Setting this still allows for duplicate revisions to be sent to a webhook URL, if a previously winning revision is made the winner again (after tombstoning the current winning revision/branch). Clients still need to ensure they have appropriate handling for duplicate events.

https://docs.couchbase.com/sync-gateway/current/configuration-schema-database.html#event_handlers

https://docs.couchbase.com/sync-gateway/current/webhooks.html
 

Example of this in use in a SG database config:

{    

    "bucket": "b1",

    "num_index_replicas": 0,

    "event_handlers": {

        "document_changed": [

            {

                "handler": "webhook",

                "url": "http://127.0.0.1:49571?event=WinningRevChanged",

                "options": {

                    "winning_rev_only": true

                }

            }

        ]

    }

}