* initial invoke testing
this assures that Content-Type and Fn-Http-Status are set for an http-stream
function. it took some fixing up of the test utils code for the plumbing to
work, looking forward to deleting most stuff in fn-test-utils.go file around
each format -- had to update fdk-go to latest for http-stream support. this
only adds 1 test, since there's some machinery here, and would like to unblock
working on the http gateway simultaneously while adding a full suite of invoke
tests (this work can be parallelized)...
i added debug logs back to the debugging output. turns out this is useful, but
it can get noisy (only when things fail, hopefully).
* fix oom tests?