[OpenAPI-2.1] Script retrieval of latest OpenAPI spec files

Write configurable (so that it can be used by card-frontend too) script to:

• retrieve openapi.yaml from master:latest for each appropriate API repo
• document hashes so that the source of this file can be confirmed/determined later
• optionally[1] commit appropriate spec files

Use it to pull all specs and commit them as initial set.

[1] - optional so that CI can use the same script when performing a comparison