Implement and test backend student task view workflow

[XiangjunMi832]

What was implemented

• Hardened the student task list and detail endpoints
• Built student task responses from existing Expertiza model relationships instead of a standalone task table
• Enforced authentication and ownership checks so students can only access their own task data
• Preserved the legacy student task detail endpoint for compatibility
• Added student revision request submission
• Added instructor revision request review flow:
  • list revision requests for an assignment
  • view a revision request
  • approve or decline a pending revision request
• Reduced the student_tasks routing surface to the endpoints actually supported by this backend

Student task response data

The backend task payload now includes:

• assignment and course metadata
• team and team member data
• topic / project topic data
• deadlines and timeline data
• review feedback
• submission feedback
• latest revision request state
• can_request_revision for action gating

Tests added

Request specs

• successful task list retrieval
• successful task detail retrieval
• empty task list
• unauthorized access
• forbidden access to another student's task
• invalid task IDs
• legacy /student_tasks/view behavior
• successful revision request creation
• duplicate pending revision request rejection
• rejection when revision requests are not allowed
• instructor listing of revision requests
• instructor/student visibility checks for revision requests
• instructor approval and decline flows
• invalid revision request IDs and invalid statuses

Model specs

• StudentTask composed payload building and serialization
• StudentTask deadline parsing and revision eligibility rules
• RevisionRequest validations and duplicate pending request prevention

Routing specs

• student_tasks
• revision_requests

Verification

docker compose run --rm app bundle exec rspec spec/requests/api/v1/student_tasks_controller_spec.rb spec/requests/api/v1/revision_requests_controller_spec.rb spec/models/student_task_spec.rb spec/models/revision_request_spec.rb spec/routing/student_tasks_routing_spec.rb spec/routing/
revision_requests_routing_spec.rb

Result:

56 examples, 0 failures

## Notes

This PR covers the backend scope only.

[github-actions]

	3 Warnings
⚠️	Pull request is too big (more than 500 LoC).
⚠️	Schema changes detected without a corresponding DB migration.
⚠️	RSpec tests seem shallow (single it blocks or no context). Consider improving test structure.

Generated by 🚫 Danger