feat: adds support for custom labels

[gaganhr94]

Fixes #75

• The PR adds support to customLabels. Any label mentioned under this would apply to all the kubernetes resources defined in the helm chart.
• As per the discussions and recommendations made in PR Feat/add common labels #62, the changes have been made and this is the new PR for it
• Bumps up the chart version to 0.8.0
• Upgrades the AppVersion to v1.0.1 (latest GUAC version)
• Updated README for the these changes as well as a few minor fixes
• You will see the guac.labels replacing guac.selectorLabels in a few places. guac.labels includes guac.selectorLabels, in other words it is a superset of the selectorLabels. So as a part of this change, since customLabels are also a part of guac.labels now, it had to be placed in all labels section. Having both labels and selector labels would create duplicates, to avoid that, this change of replacing guac.selectorLabels with guac.labels has been done

[gaganhr94]

Hi @sunnyyip @pxp928 can you please review this PR when you get a chance. Thanks !

[lumjjb]

one of the concerns i have is how others are currently using selectorLabels. This may break some users. is there a way we can add an error message for users that use selectorLabels will get a message about the new change to the new labels?

[gaganhr94]

If you see the _helpers.tpl, guac.labels includes guac.selectorLabels. Whenever we refer to guac.labels, it will always include the guac.selectorLabels

{{/*
Common labels
*/}}
{{- define "guac.labels" -}}
helm.sh/chart: {{ include "guac.chart" . }}
{{ include "guac.selectorLabels" . }}            <-- here
{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- if .Values.guac.customLabels }}
{{ toYaml .Values.guac.customLabels }}
{{- end }}
{{- end }}

{{/*
Selector labels
*/}}
{{- define "guac.selectorLabels" -}}
app.kubernetes.io/instance: {{ .Release.Name }}
app.kubernetes.io/part-of: "guac"
{{- end }}

This is the main reason why guac.selectorLabels had to be changed to guac.labels, since having both them under the pod template labels would create unnecessary duplication of the same labels.

So, I don't see it breaking for the existing users of GUAC helm chart. It's just that the pod may have a few more labels than expected.