Workers should ignore tasks which already been run twice. To achieve this, a column execute_count is added to CE task tables which will be incremented each time a task's status is changed to "IN_PROGRESS"
Add execution_count column to CE_QUEUE and CE_ACTIVITY tables as a NON_NULL INTEGER.
The value of this column is 0 when a new line is inserted.
- a newly created task (ie. with status "PENDING") has execution_count = 0
- a task "IN PROGRESS" always has a execution_count > 0
- a task "PENDING" may have execution_count > 0 if it has already been executed at least once
- tasks created in this table prior to this ticket have execution_count = 0
- a "CANCELED" task may have execution_count > 0
- tasks with status "FAILED" and "SUCCESS" always has execution_count > 0