feat(artifacts): Add support for helm/chart artifacts

[eromanova]

Issue: spinnaker/spinnaker#3284

[eromanova]

@spinnaker/reviewers review, please

[jfillo]

I'm not an official reviewer, but I think there should be some changes to allow the Halyard CLI to manage this configuration.

See

• https://github.com/spinnaker/halyard/blob/master/docs/commands.md#hal-config-artifact
• https://github.com/spinnaker/halyard/blob/master/halyard-cli/src/main/java/com/netflix/spinnaker/halyard/cli/command/v1/config/artifacts/ArtifactProviderCommand.java
  and whatever additional code paths need to be followed.

Also - features like this should also include a PR to update the official documentation. https://www.spinnaker.io/setup/artifacts/

[ezimanyi]

Looks good! As @jfillo noted, you'll want to add the HelmArtifactProviderCommand so this can be configured via the command line.

The documentation will actually auto-generate once you've added that if you run make from the halyard-cli subdirectory; you can just submit those auto-generated docs along with the rest of the changes.

[ezimanyi]

Looks like we could push this up to the base class in ArtifactProvider. (I realize all the existing accounts have overridden it, but seems like a good opportunity to avoid duplicating the code again.)

[eromanova]

Thank you for review, guys @ezimanyi @jfillo. I added halyard cli support for helm artifact acconts and provided small changes according to @ezimanyi comment. Docs are also updated.

[ezimanyi]

@eromanova : Looks great, thanks for the changes.