Expand and Contract pattern with examples
What does this MR do?
Reading the changes in !37550 (merged) I realized we are collecting outage examples but our documentation doesn't explain how to avoid them.
I think that this merge request is the first attempt at providing a bit of explanation on the theory behind safe continuous deployment, providing examples of solutions.
All those examples keep in mind that even if we deploy daily, we still have to support zero-downtime upgrades for customers.
Related to gitlab-com/gl-infra/delivery#1086 (closed)
Edited by Alessio Caiazza