add UUID.from_bin
blanket switch to canonical UUIDs
clean-up Receiver spec
simplify Messages specs
clean-up Project spec
clean-up Task spec
clean-up Repo spec
clean-up Registration spec
clean-up Registrar spec
clean-up Repos spec
clean-up Client spec
UUID.from_bin → UUID.[]
Registration#{from,to}_h: (de)serialise client + project
Repos: add Registration support
add Result#uuid
simplify Receiver spec
add Result#to_h
add Result.from_h
Repos: add Result support
refactor Repos spec