* LRS-70 sketch out current multipart validation behavior with some tests

* LRS-70 add cljs dispatch for exinfo

* fix requires in lrs-test

* LRS-72 clean up and refactor in prep to decouple sig checking

* LRS-72 don't slurp in cljs

* LRS-72 make an xapi fn for pulling att objects generally with statement + path

* LRS-72 additional testing on current multipart behavior

* LRS-72 validate multiparts, handle dup input and dedupe output

* LRS-72 impl notes for attachment batches

* LRS-72 added to impl note

* LRS-72 extract big blobs from sig test

* LRS-72 better error for missing attachments + test

* LRS-72 refactor reduce-fn for validate-multiparts