Pages Editor: add "Delete Task from Page" functionality

[shaunanoordin]

PR Overview

Part of: Pages Editor MVP project and FEM Lab super-project Follows #7065 Staging branch URL: https://pr-7075.pfe-preview.zooniverse.org/lab/1982/workflows/editor/3711?env=staging

This PR implements the "Delete Task" functionality, which deletes Tasks from an existing Page. Prior to this PR, you only had the "Delete Page/Step" functionality.

New Behaviour:

• Tasks in the "Edit Page/Step" modal should now have a "Delete Task" button (trashcan icon).
• Clicking on the button will prompt users to confirm if they want to delete the task.
  • If this is the only task in a page/step, additional information will be given.
• Confirming the action will result in the Task being deleted.
  • Cancelling will result in no action.
  • If the only task in a page/step is deleted, the page/step will also be deleted. The Edit Page/Step modal will then close.

⚠️ Important Behind-The-Scenes Bit:

• cleanupTasksAndSteps() now properly removes Steps/Pages that have 0 Tasks, and removes Tasks that aren't associated with any Page/Step.

Testing Steps

• Go to the testing URL: https://pr-7065.pfe-preview.zooniverse.org/lab/1982/workflows/editor/3711?env=staging
• Click on "Quick Setup" in the debug panel to quickly setup a pre-fabricated workflow.
• Click on the "Edit Page/Step" button (pencil icon) to edit any Page/Step
  • Optional: add new Tasks to this Page/Step.
• In the "Edit Page/Step" modal, click on the "Delete Task" button (trash can icon) to delete any Task.
  • Observe that Task is correctly removed from the Page.
  • If the Task removed is the last one in the Page, the Page should also be deleted and the Edit Page/Step modal should close.
• Confirm that changes to the Workflow resource is correct (i.e. check what's submitted to the Panoptes API).
  • Be sure that there are no orphaned references.

Status

Ready for review!

[coveralls]

coverage: 56.977%. remained the same when pulling 22dcb1540ae5ec9ffdbd7a781be695d2ee9ed5bd on pages-editor-pt19 into a82d2f148d791a762c9aab145b139145923c8553 on master.

[shaunanoordin]

Thanks Delilah! 👍