Draft: Run a deployment check report during the gprd promotion check
What does this MR do?
This creates the initial Slack thread for posting progress messages, rather than relying on a hard-coded "gprd-migrations 50%" message which may never be sent, depending on the number of migration hosts we have in the fleet.
Resolves gitlab-com/gl-infra/delivery#1987 (closed)
Author Check-list
- [-] Has documentation been updated?
Edited by Robert Speicher