Update the checkpoints table with `FlowIORequest` information. This is a separate database commit that runs on a schedule to update the `flow_io_request` column.
We might want to batch multiple update statements into a single database commit.
`FlowMonitor` should be updated to perform these updates. At the moment it just logs but the logic around what flows to log information about is exactly what we need for this task.
`flow_io_request` will be set back to `null` when a flow completes its next successful transition (next database commit). This being set and become null again should be tested.