Dataweave Example using map, flatMap, distinctBy & orderBy

gistfile1.txt

%dw 2.0
output application/json
---
payload
map ((item, index) -> item.ErrorDetail.ValidationMessages) // Extract ValidationMessages from each item
flatMap ($) // Flatten the array of arrays into a single array
distinctBy ($.Message) // Remove duplicate messages based on the Message field
orderBy ($.Message default "")
map ($.Message) // Extract just the Message field