Record transitions + errors of batched jobs (Gitlab logs)

We only have the last snapshot of the batched background migration job object. We are not able to see the event transition history. Not having this information recorded is terrible because sometimes we need to debug issues that happened in the past, and we don't have any records. Also, this data could be helpful for product managers. They will be able to extract information about what happened during the execution of a batched background migration.

I suggest that we record every transition + (error) in Gitlab logs.

This gem could help us achieve the goals proposed before. It has a simple API for state and transition definition, and it is already used in Gitlab.