Separate "instance of service" from "database"
Then there should be a
kv_database_t object that contains the hg_handle_t fields, along with the server address. The
kv_open function should return a pointer to such a
kv_database_t. Its signature should be the following:
kv_database_t* kv_open(const kv_context_t *context, const char *server, const char *db_name)
kv_close function should take a
kv_database_t* instead of a