[service] enforce that Service argument and return are json-serialisable
The call_service API need to be able to run through RPC. So we ensure front
start that it is possible serialise both input and output.
Latest changes
--------------
* table of `all latest changes`_
Links below is providing useful RQL query example.
.. _all latest changes: view?rql=Any+M%2CX+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30