Create spec to document current behavior for `platform_id`
Create spec to document current behavior for `platform_id`

[#166241318]

https://www.pivotaltracker.com/story/show/166241318

concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse