feat(values) add fullnameOverride

[rainest]

What this PR does / why we need it:

Adds a full name override.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes Add support for fullnameOverride to Chart #157

Special notes for your reviewer:

Compare:

10:56:40-0700 esenin $ helm template --namespace default aaa /tmp/symkong -f ~/src/charts/charts/kong/example-values/minimal-kong-enterprise-dbless.yaml --set fullnameOverride=ccc 2>/dev/null | grep -A2 "kind: Service" | head -3 
kind: ServiceAccount
metadata:
  name: ccc
10:56:57-0700 esenin $ helm template --namespace default aaa /tmp/symkong -f ~/src/charts/charts/kong/example-values/minimal-kong-enterprise-dbless.yaml --set nameOverride=ccc 2>/dev/null | grep -A2 "kind: Service" | head -3 
kind: ServiceAccount
metadata:
  name: aaa-ccc
10:57:08-0700 esenin $ helm template --namespace default aaa /tmp/symkong -f ~/src/charts/charts/kong/example-values/minimal-kong-enterprise-dbless.yaml 2>/dev/null | grep -A2 "kind: Service" | head -3 
kind: ServiceAccount
metadata:
  name: aaa-kong

nameOverride was originally entirely undocumented; it and this are now in the readme but I've left them out of values still.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• PR is based off the current tip of the main branch.
• Changes are documented under the "Unreleased" header in CHANGELOG.md
• New or modified sections of values.yaml are documented in the README.md
• Commits follow the Kong commit message guidelines

[pmalek]

One small comment on this though: we might want to consider failing on templates rendering when .Values.fullnameOverride is longer than 63 characters since that might cause problems.

[rainest]

It'll fail to apply resources. I figured we shouldn't truncate the "use exactly what I provide, no additional formatting" one since the remediation there should be that you choose a new, acceptable name of your own.

[pmalek]

Not sure if I understood but my proposal was not to truncate the full override but to fail and "return an error" (to the extent possible with helm).