Add support for :key-fn in wrap-json-body middleware.

[benjamincassidy]

Add support for a :key-fn to the wrap-json-body middleware which is passed to cheshire to convert keys.

[bigwheels16]

Although it's not documented, you can pass a function as the :keywords? value:

(def app (-> routes
                      app-routes
                     (wrap-json-body {:keywords? #(keyword (.replace % \_ \-))})))