Add a new mock type for fuzz testing

[gwleclerc]

As people are talking a lot about fuzzing at the moment with the introduction of fuzzing tests directly in golang with 1.18, I'm asking myself if we could add a fuzz mock ? It could took a json as a template body and fuzz it using by example https://github.com/google/gofuzz to randomize a bit the return.
We could also randomize status code and latency.