First, thanks for great CQRS framework.
I really admire your work.
On wiki page of Axon-trader example:
there is said that:
“When receiving a command to create a new user,
we first check against a special collection to see if the username is still available.
After validation we actually create the user.”
… but there is no such a logic in related command handler:
Maybe I missed something but I could really use a reference solution for this problem.