The compiled functions implement that interface which means you can inspect
the signature of the method that created them and discover its
generic types.
Compiled functions always show up with no metadata, and you can only
guess what the types are from the bean definition. Probably we should
add more information to the bean definition if we have it when we
compile the function.
There is still a problem if user defines functions that are not of
Flux<String> (but that has always been the case).
Make it deployable via its maven coordinates in
spring-cloud-function-deployer (it is deployed by default on start
up right now, but that's just a demo)
