This will serialize the arguments into JSON, just like Sidekiq would
for calculating the `#idempotency_string` and checking for duplicate
jobs.

This would be a more robust approach, because serialization of for
example symbols would currently be different when serialized on the
clientside versus after they have been loaded from redis.

It would not have affected anything on a running instance, because the
key is already serialized into the job hash and checked like that in
Sidekiq server.