users shouldn't need to know the full API entrypoint(s)

[thomas-fossati]

Since we do know the entry points for endorsement and evidence submission (they are fully specified by the API documentation) we shouldn't require the user of the package to specify the full URI, only the base. I.e., rather than https://veraison.example/challenge-response/v1/newSession, the user should supply https://veraison.example/challenge-response/v1. (The same for the endorsement API).

[thomas-fossati]

For endorsements SubmitConfig.SubmitURI should be renamed to SubmitConfig.BaseURI and the /submit path segment automatically appended to it. (Same for ChallengeResponseConfig.NewSessionURI, except the path segment is /newSession.)