http modules could only fire independent one-shot requests: an extractor
recorded a value for reporting, but nothing could feed it back into a
later request. add a requests: chain where steps run in order sharing a
variable map, so a step's extractors populate {{name}} references in the
path, headers and body of later steps.
a step with matchers records a finding on a match and halts the chain on
a miss, so a login or setup step can gate an authenticated follow-up. the
single-request form is unchanged and stays the concurrent default when no
chain is defined.
Co-authored-by: vmfunc <vmfunc.lc@gmail.com>
