Validate number of nodes for f1-micro when creating GKE cluster
Problem to solve
Resolve a common issue where creating a GKE cluster of fewer than 3 nodes of f1-micro will error out, but only display a generic error to the user.
Further details
As part of https://gitlab.com/gitlab-org/gitlab-ce/issues/38759, we introduced some front-end improvements as well as some client-side validation to improve the experience and reduce the error rate of creating GKE clusters.
Undocumented in Google's Cloud API, you cannot create a cluster of f1-micro nodes if the number of nodes is fewer than 3.
Proposal
Extend the existing client-side validation to check whether the number of nodes is greater than or equal to 3, when using the f1-micro machine type.
What does success look like, and how can we measure that?
You can no longer create a GKE cluster of fewer than 3 f1-micro nodes, and have a greater chance of success when creating a GKE cluster.