Re-serialise and combine check results
checks_utils we are already able to convert check results to JSON for use with the API and for better long-term storage. This includes a custom format for histogram serialisation (in !56 (merged)). However LbAPCommon is currently missing a central method of serialising this JSON.
This would be needed if the results of multiple checks are to be combined, eg. histograms can easily be added as
hist objects. Combining results will be very useful for offline monitoring, as checks can be run in small frequent batches and then combined as needed without needing to re-run the checks over full datasets each time.