[p3t] More experiments with OpenAPI schema

[Russ Allbery]

I've made a version of the previous 3.1.0 OpenAPI schema for cone-search
that uses OpenAPI 3.0.3 instead, and have pushed that up to the
repository.

I successfully used that to generate a Rust client, using OpenAPI
Generator (https://openapi-generator.tech/docs/installation).  The
resulting code looks reasonable.  It's a bit awkward and certainly errs on
the side of long names for everything, but all the types seem correct and
are plugged into serialization the way that I would expect.  I'm still not
sure that I would directly use the generated code for anything other than
a starting point, but it's a reasonable starting point.

It was a bit hard to find a Rust OpenAPI code generator that actually
worked.  None of paperclip, progenitor, or swagger-codegen accepted the
schema, all with extremely unhelpful and cryptic error messages, even
though the on-line Swagger editor said it was warning-free.  But OpenAPI
Generator worked fine.

-- 
Russ Allbery (eagle at eyrie.org)             <https://www.eyrie.org/~eagle/>