sla draft support

[vtolstov]

What you think about supporting https://github.com/isa-group/SLA4OAI-Specification/blob/main/versions/1.0.0-Draft.md ? My use-case - allow to specify in proto/openapi timeout for each endpoint

[timburks]

I'd be open to it - I've been participating in discussions around SLA4OAI. In the first year or so of gnostic, we had a contribution that built support for schema extensions (see the extensions directory). To my knowledge, that hasn't gotten any use, so I've been thinking about removing it, but it could be a good way to support the SLA4OAI specification - essentially we would use a JSON schema of the specification extension to generate protos and parsing code that could then be called from gnostic as a plugin.