Argo CD stack update

[v-ctiutiu]

Description

Argo CD is another popular open source implementation providing a neat GitOps experience. One of the main features making it unique amongst other existing solutions (like Flux CD for example), is the ability to audit and observe all CD pipelines via a graphical web interface.

Currently, the 1-click marketplace app installs and checks Argo CD installation via kubectl commands. We can enhance and simplify the process by using Helm. An official Helm chart is available now for Argo CD on the argo project repository.

Impacted Areas

None.

Solution

As per the contribution guideline, following steps must be performed:

1. Use the stack generator script provided in this repository (./stack-templates/generate-stack.sh), and have the required scripts created automatically.
2. Tweak as necessary the Helm chart values inside the values.yml file (usually we don't paste here the default values, because those will be merged anyways from the upstream values file of the Helm chart).
3. Validate that the scripts work as expected for each scenario (deploy/upgrade/uninstall).
4. Have the main README created, containing a quick start guide for Argo CD.

[v-ctiutiu]

Fixed via #357.