Also applies to output types, wrapper types and identifying if
messages can be processed directly.
See gh-81 (the ambiguity is still there, but the indirection bug
is fixed).
The FunctionInspector needs to be able to distinguish between a
function of Flux<Foo> and a function of Flux<Message<Foo>>. Then
it can do the conversion a level below.
Only supports Message->Message or POJO->POJO (no mixtures), so there
is only one new method in FunctionInspector.
No support in the web endpoints yet. But it's probably not so hard
to add.
The compiled functions implement that interface which means you can inspect
the signature of the method that created them and discover its
generic types.
