Migrate MOOC GitLab from OVH to DigitalOcean

OpenCraft is migrating our infrastructure off OVH and onto DigitalOcean, and so part of this migration includes migrating the gitlab.courses.opencraft.com service that is used by this course.

This change will involve:

• Gitlab data migration to the new instance
• Updates to the ansible & terraform infrastructure for this service.
• ⚠ An outage to the gitlab.courses.opencraft.com service during the migration.