Issue Promotion Failing Due to Timeout on System Notes

Problem

Issue promotion (both via UI Change Type option and /promote quick action) is failing with timeout errors when attempting to promote issues that have a large number of system notes. The promotion process times out during the notes copying operation within the 60-second request limit.

/promote command returns errors: "Unexpected token '<', "<!DOCTYPE "... is not valid JSON" followed by various timeout messages

Root Cause

The current promotion process uses IssuePromoteService with legacy Issuable::Clone::BaseService, which copies system notes one at a time within a single transaction. For issues with many system notes, this operation exceeds the request timeout (60s) and causes the promotion to fail.

Proposed Solution:

Migrate issue promotion to use DataSync services, which:

• Perform bulk operations instead of individual note copying
• Are more optimized for large data transfers
• Should reduce the likelihood of timeouts

Optimally, we should move these operations in background jobs. However, to not re-invent the wheel, I'd rather wait for &16152 (closed) to be completed.

Additional Considerations:

Potential concurrency issues when multiple users promote the same issue simultaneously. We need to handle cross-project/group cloning restrictions for Epic promotion.