Job archival:

• Sets job status "archiving"
• For each task, de-chunks the task logs and gz-compresses them.
• Creates a ZIP file with the job+task definitions in JSON and compressed logs.
• Uploads the ZIP to the project's file storage.
• Records the link of the ZIP in the job document.
• Deletes the tasks and task logs in MongoDB.
• Sets the job status to "archived".