Notify partner contributors to fill in the new gitlab username info
## Summary
We have a new gitlab username column in the planning sheet. We need contributors to fill it in. It will be used for reporting.
## Work Track
Cross-track / Development
## Tasks
- [x] Send email to all partners via accountable list
- [x] Send Slack message in partners and contributors channels
- [ ] Check for gaps in a few days and follow-up directly
issue