Pass more context from Sidekiq jobs to Logster

Using the new recommended Sidekiq -> Logster reporter from [here](https://github.com/riking/logster/blob/clear/lib/examples/sidekiq_logster_reporter.rb)
@SamSaffron said:

> interesting, this is appending an error handler ... is the original blank? do we need this chained?

Well, it's probably fine, seeing as you added this code in the first place: https://github.com/riking/discourse/commit/4af0aa9cbcd1c703b097534c8f7baefc36e158f8#diff-fd9e64e4a154ab77edea808fa4285141R45