Add warnings if due dates can't be shifted when importing assignments

[oscarlevin]

Courtesy of my assistant, this makes importing assignments more robust: if a due date for an assignment cannot be shifted (for example because the course timezone is not supported), then the assignment is still imported, just not with a shifted due date.

[Copilot]

Pull request overview

This PR makes assignment importing more resilient by allowing imports to proceed even when due-date shifting fails (e.g., because a course timezone is invalid), and surfaces warnings so instructors know to review due dates.

Changes:

• Update due-date shifting to return an optional warning instead of raising when a course timezone cannot be resolved.
• Propagate duedate_warning / duedate_not_shifted through backend import APIs and into the assignment builder UI.
• Add coverage for invalid-course-timezone behavior in the assignment sharing/import tests.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/components/rsptx/db/test_assignment_sharing.py	Adds test ensuring imports succeed and return a warning when timezone resolution fails.
components/rsptx/db/crud/assignment.py	Implements warning-returning due-date shifting and threads warning/count through import flows.
bases/rsptx/assignment_server_api/routers/instructor.py	Adds warning/count fields to instructor import API responses.
bases/rsptx/assignment_server_api/assignment_builder/src/types/assignmentSharing.ts	Extends TS types to include duedate_warning and duedate_not_shifted.
bases/rsptx/assignment_server_api/assignment_builder/src/store/assignment/assignment.logic.api.ts	Displays informational toasts when due dates could not be adjusted.
bases/rsptx/assignment_server_api/assignment_builder/src/components/routes/AssignmentBuilder/components/importAssignment/ImportPreviewPanel.tsx	Shows an inline warning alert in the import preview when due date couldn’t be adjusted.
bases/rsptx/assignment_server_api/assignment_builder/src/components/routes/AssignmentBuilder/components/importAssignment/ImportAssignmentModal.spec.tsx	Updates preview mock to include duedate_warning.
bases/rsptx/admin_server_api/routers/instructor.py	Includes warning/count details in admin “copy assignment(s)” responses/messages.

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[bnmnetp]

@oscarlevin -- can you fix the lint issues, and then I'll work on getting this out ASAP.

[oscarlevin]

Yes, although it will not happen until this evening when I'm home from my day job. :(

[bnmnetp]

OK, I may just fix it on my end (easy enough) so I can get this out. Its creating some anxiety for the CSAwesome teachers.

[oscarlevin]

Thanks, sorry I lost track of this yesterday. Busy time of year.