buffet: Add support for 'additionalProperties' attribute

GCD server requires parameters of type 'object' to include the
'additionalProperties' attribute in their schema. This attribute
has been implemented in buffet internally but never exposed through
JSON, so here we add both serialization and de-serialization code
for 'additionalProperties'.

BUG=brillo:356
TEST=`FEATURES=test emerge-link buffet`

Change-Id: I8db3144e2e572b1835d34603be3677a82734c679
Reviewed-on: https://chromium-review.googlesource.com/263270
Trybot-Ready: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Aaron Kemp <kemp@google.com>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
5 files changed
tree: 09c1d3cfef691d47eb0638c58f1be3a3e7484e05
  1. buffet/