Detect misspellings in request bodies

[Ben Sayers]

Situation: * A swagger defines a property as optional in the request body * A swagger allows additional properties in the request body * The pact file contains a mis-spelling of the optional property

In this case the mis-spelled property will be treated as an additional property and so the validation will not fail.

The desired behaviour would be to have a warning generated to indicate the additional property may not be desired behaviour.

[Ben Sayers]

Fixing this introduces a lot of complexity, more example incidents where this would have helped are required to justify taking this on.