Data source full_message instead of message field

[xeiss]

I have an input with an JSON string on full_message and a human readable text on message field.

I want to use this plugin to output the JSON string from the full_message field to another system.
But all message formats (plain, transparent, ...) use the message field as a data source. So in my case only the human readable text will send to the destination.
The message format "full" outputs all fields, but I only need to output the full_message field.

I think a perfect solution would be a option in the "Editing Output" dialog, where I can configure which field should be used as data source. But for me a checkbox with "Use full_message instead of message" would be sufficient.

I use Graylog 4.2.7 and Plugin Version v4.2.6.