Add command to render a Go template

[wyvernzora]

For context, see kairos-io/kairos#1907.

Added a command kairos-agent render-template -f <templatefile> that reads in a Go template file and renders it.
It sets the following as data context available to the template:

• Config: the Kairos configuration object (kairos-agent config get)
• State: the Kairos state object (kairos-agent state)

Any feedback is welcome.

Example

# cloud-config
kubevip:
    eip: 192.168.1.1
    enabled: true
    interface: ens18

# template.yaml
apiVersion: helm.cattle.io/v1
kind: HelmChart
metadata:
  name: kube-vip
  namespace: kube-vip
  annotations:
    test: "{{.State.uuid | trunc 8 | upper}}"
spec:
{{- with .Config.kubevip -}}
  chart: kube-vip
  repo: https://kube-vip.github.io/helm-charts
  version: "{{default "0.4.4" .version}}"
  valuesContent: |-
    config:
      address: "{{.eip}}"
    env:
      vip_interface: "{{.interface}}"
      cp_enable: "{{default "true" .enabled}}"
{{- end -}}

$ ./kairos-agent render-template -f template.yaml
apiVersion: helm.cattle.io/v1
kind: HelmChart
metadata:
  name: kube-vip
  namespace: kube-vip
  annotations:
    test: "2AA2FAA5"
spec:chart: kube-vip
  repo: https://kube-vip.github.io/helm-charts
  version: "0.4.4"
  valuesContent: |-
    config:
      address: "10.10.19.0"
    env:
      vip_interface: "ens18"
      cp_enable: "true"

[codecov]

Codecov Report

Merging #159 (f26a517) into main (01e0a00) will decrease coverage by 0.02%.
The diff coverage is 55.55%.

@@            Coverage Diff             @@
##             main     #159      +/-   ##
==========================================
- Coverage   58.69%   58.68%   -0.02%     
==========================================
  Files          37       38       +1     
  Lines        4656     4683      +27     
==========================================
+ Hits         2733     2748      +15     
- Misses       1691     1699       +8     
- Partials      232      236       +4     

Files	Coverage Δ
pkg/action/render_template.go	55.55% <55.55%> (ø)

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[jimmykarily]

Good job! Just a comment to add a test for this. We will also need to document this when we merge it.

[wyvernzora]

Updated the PR and rebased the branch.

[jimmykarily]

Good job!