How can I deal with axon in a scenario where the aggregate identifier exists only after an entity was created by an external system? Seems like I wont be able to send the command from the client since I do not have the id yet.
Can I still use an (external) commandhandler with reference to the aggregate repo? do I have to work with two commands (create external resource triggers create-aggregate command)? Can I work with a custom UnitOfWork? Would Saga be an option?
Background: I want to use axon aggregate to synchronize writes to the underlying system to benefit from locking and projections but cannot refactor the whole application to use aggregates/ES completely.