Service Layer
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When a submission is created the value is false.
Add CANCELED as a submission status in the ss enum.
The field is mapped to a 'public' annotation in the query table.
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Add a leaderboard widget, including an executionStatus column. The query should use 'where userId==@CURRENT_USER' to show just the submitter's jobs.
Choose the 'stop button' renderer for this column.
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