add artifact attestation

[DrFaust92]

closes #409

tested locally from fork:

[GMartinez-Sisti]

Seems like we have an issue with unittest -> helm-unittest/helm-unittest#777. Let's follow up for some days and see if it gets solved.

[DrFaust92]

GMartinez-Sisti can we pin it to helm 3 meanwhile?

[GMartinez-Sisti]

GMartinez-Sisti can we pin it to helm 3 meanwhile?

Since the unittest repo is fairly active, I'd rather wait another week or so. This is a nice extra but AFAIK no one is blocked on this.

[DrFaust92]

@GMartinez-Sisti seems that many did this https://github.com/FlowFuse/helm/pull/747/files. wdyt?

[GMartinez-Sisti]

@GMartinez-Sisti seems that many did this https://github.com/FlowFuse/helm/pull/747/files. wdyt?

→ helm plugin install -h | grep -- "--verify"
Use --verify=false to skip signature verification for remote plugins.
      --verify                     verify the plugin signature before installing (default true)

Decreasing the security of the CI tests to provide artifact attestation feels a bit contradictory 😅 Atlantis is an application with the highest level of permissions given its nature. I think it's safer to wait.

We should be able to merge this soon! Thank you for all the help 🙏