Clarify support for Kubernetes versions older than 1.19
Summary
https://docs.gitlab.com/charts/installation/cloud/index.html states that Kubernetes versions 1.20-1.25 are currently supported by the GitLab chart, but further down the page notes
Disabling the in-chart NGINX Ingress Controller (nginx-ingress.enabled=false), allows the use of Kubernetes 1.16 or later. Alternatively, using version 1.2.1 (nginx-ingress.controller.image.tag=v1.2.1) allows the use of Kubernetes 1.19 or later.
This note implies, but does not state that we support Kubernetes 1.16 and later, including 1.19. This page links out to the operator page that says Kubernetes 1.19-1.22 are supported. The agent cluster version support page links back to the chart and operator pages.
We need to update this documentation to clarify these questions:
- Do we support Kubernetes 1.19 for GitLab chart? If so should include that in the range in the page,
1.20-1.25->1.19-1.25and retain the note on nginx config for 1.19 - De we support Kubernetes 1.16-1.18 as well for the GitLab chart? If so, we don't run these versions for CI so a lot of manual work is being done to verify compatibility that we should discuss. If not, we should remove the part of the note on the page that references Kubernetes 1.16.
Followup from discussion in MR gitlab-org/build/CNG!1582 (merged), about how far back in Kubernetes versions to test a kubectl update.