Replace UnaryHandler from structure to method arguments in order to reuse
single instance for different service methods.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
Defines ServiceExecutor interface of the executor that handles service
request bodies and returns service response bodies. Adds Service
implementation that writes the result of ServiceExecutor to response body
and attaches the internal ResponseMetaHeader.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
Adds accounting Service implementation that verifiers request signatures and
signs responses from internal Service.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
