Use request's host in error result's absoluteKeywordLocation

[karenetheridge]

If the openapi document is constructed with a relative URI as its identifier, there is an opportunity to resolve this URI at runtime when generating errors so the stated location of the document uses the same host as that used in the original request, so the caller has an absolute URI as a reference for the document used to generate the error.

• JSM::evaluate() needs to accept a base_uri at runtime, as a config_override (3rd argument)
• capture $request->uri->host when $request and $response initializes its $state, and pass this value to JSM::evaluate

'servers' information in the document should be taken into account, e.g.:

• servers: specifies a base uri of "/v1"
• path-item: specifies an operation with path "/foo/bar"
• openapi document is configured with a canonical uri of "/api"

therefore an incoming request with uri "http://example.com/v1/foo/bar" is routed to this operation, and errors will use absoluteKeywordLocation: "http://example.com/v1/api#/path/to/error"

[karenetheridge]

This is now done (except for looking at the servers config) in 0.021.