multimethod entrypoint for server construction

reads the body of the request can be expanded

(-read-body “{:a 1}” :edn) => {:a 1}

read the string value of the datastructure according to format

(-read-value “{:a 1}” :edn) => {:a 1}

writes the string value of the datastructure according to format

(-write-value {:a 1} :edn) => “{:a 1}”