[CLXR-462][S] Add carrer offline sync

[Ahmed-Naguib93]

feat: add offline sync
refs: CLXR-462
builds: student
affects: student
release note: none

1. Adds Horizon-specific background offline sync infrastructure to the Canvas Career (Horizon) experience
2. Introduces HSyncBackgroundTask that iterates logged-in sessions, refreshes course data in the background, and restores the previously active session on completion
3. Adds HSyncNextDateInteractor and HSyncAccountsInteractor to calculate which sessions are due for sync and when the next background task should fire
4. Adds HSyncScheduleInteractor to schedule/reschedule the BGProcessingTask after each sync cycle
5. Stores Horizon sync preferences (frequency, nextDate, autoSyncEnabled, offlineSyncItems) in SessionDefaults per user session
6. Registers the background task identifier (com.instructure.icanvas.horizon-sync) in Info.plist and StudentAppDelegate
7. Routes background sync scheduling in applicationDidEnterBackground based on whether the active app is Horizon or Canvas Academic

[claude]

Review: Horizon Offline Sync Background Task

Overall the implementation is clean and follows existing project patterns well. Good test coverage across the new interactors. A few issues worth addressing:

---

Issues

• Failed syncs update the next-sync date as if they succeeded — HSyncBackgroundTask.syncNextSession (HSyncBackgroundTask.swift ~line 57): the receiveCompletion closure is invoked for both .finished and .failure(_:) without distinguishing between them, so scheduleInteractor.updateNextSyncDate is called even when the network call fails. This pushes the next sync window forward even though no data was actually refreshed.

• Concrete class subclassing used for mocking instead of protocols — HSyncNextDateInteractor and HSyncScheduleInteractor are public class types that the test suite mocks by subclassing (MockHSyncNextDateInteractor: HSyncNextDateInteractor). This is a testing anti-pattern that prevents the classes from being final and tightly couples the tests to the concrete implementations. Prefer extracting a protocol (e.g. HSyncNextDateInteractorProtocol) and injecting it, which is how the existing CourseSyncInteractor family is structured.

• Hardcoded uniqueID format in test assertion — HSyncBackgroundTaskRequestTests.swift line 43 asserts mock.receivedSessionIDs.sorted() == ["testurl.com-user-1", "testurl2.com-user-2"]. This bakes in the internal LoginSession.uniqueID format (host + "-" + userID). If that format ever changes the test fails for the wrong reason. A more robust check would verify that the IDs passed in match the IDs of the two sessions being used, without hardcoding the derived string.

• OfflineType.swift copyright year is 2026 — all other new files in this PR use 2025-present. Likely a copy/paste inconsistency.

• OfflineType has no access modifier — the enum defaults to internal, which may be intentional, but it sits alongside public types in the same directory. Worth confirming this is deliberate and not an accidental omission.

---

Positive notes

• The sequential-session sync loop in HSyncBackgroundTask (processing one session at a time via syncNextSession) is a sensible approach for background tasks with limited OS budget.
• SessionDefaults extensions are well-structured and consistent with existing patterns.
• HSyncAccountsInteractorTests teardown correctly resets SessionDefaults for each session, avoiding test pollution.
• Test coverage for HSyncNextDateInteractor is thorough — edge cases (empty list, disabled sync, missing date, empty items) are all exercised.

[bitrise]

	Fails
🚫	Build failed, skipping coverage check

	Warnings
⚠️	This pull request will not generate a release note.

Affected Apps: Student

Builds: Student

❌ Swift lint

----- xcbeautify -----
Version: 2.30.1
----------------------

❌ /Users/vagrant/git/Horizon/Horizon/Sources/Features/OfflineSync/OfflineType.swift:24:1: Trailing Whitespace Violation: Lines should not have trailing whitespace (trailing_whitespace)

Generated by 🚫 dangerJS against b66004f

[bitrise]

Builds

Commit: feat: add more test cases (ba12e8c)
Build Number: 1730
Built At: Apr 04 20:56 CEST (04/04 12:56 PM MDT)

Student

[bitrise]

	Warnings
⚠️	This pull request will not generate a release note.
⚠️	One or more files are below the minimum test coverage 50%

Affected Apps: Student

Builds: Student

Coverage	New %	Master %	Delta
Canvas iOS	91.89%	81.06%	10.82%
Horizon/Horizon/Sources/Features/OfflineSync/OfflineType.swift	0%	--	--
Horizon/Horizon/Sources/Features/OfflineSync/BackgroundTask/HSyncScheduleInteractor.swift	46.67%	--	--

Generated by 🚫 dangerJS against ba12e8c

[szabinst]

let's call this com.instructure.icanvas.career-sync

[szabinst]

let's call this career-offline-sync

[vargaat]

• With this if-else condition based on the currently logged in user, either academic or horizon accounts will sync but if we have mixed academic/horizon users one of them won't sync.
• If we trigger two background syncs, the OS will throttle down and one of them won't run because the background wake-up frequency would be too high.
• The academic sync logic already iterates through all accounts and syncs each one where this feature is turned on. I think the best approach would be to share the offline sync background task between the two experiences and execute the proper sync logic based on the user's experience.