Return an interface which can be converted to `io.Reader` as well as
report payload size and hash.
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
It improves payload generation in our scenarios. Current implementation
of scenarios generates single random payload at the start and then sends this
same payload on every request. More realistic test is to generate unique payload
for each request. However, this is an expensive operation that can easily cause
a bottleneck on K6 side when we run multiple writing VUs. So instead we generate
a random buffer with some extra bytes and then take slices of this buffer thus
producing a random payload for each request.
Signed-off-by: Vladimir Domnich <v.domnich@yadro.com>
