Adding the OneChart Helm chart on service creation

[laszlocph]

This PR adds a Helm chart to a newly created service. So Keptn users don't have to create a Helm chart themselves.

End-user experience:

keptn create project pod-tato-head36 --shipyard=./shipyard.yaml --git-user=laszlocph --git-token=xxx --git-remote-url=https://github.com/laszlocph/keptn-project10.git`

keptn create service myservice --project=pod-tato-head36

keptn trigger delivery --project="pod-tato-head36" --service=myservice --image="nginx" --tag="1.20.0" --values="fullnameOverride=myservice"

The deploy is then successful:

Follow-up work:

• obtaining creds somehow. Right now it is provided as env vars
• the pr uses a compatibility version of OneChart as keptn has undocumented requirements on the Helm chart format
• probably validations are needed to only add OneChart if no Helm chart was provided for the service

[github-actions]

The following Docker Images have been built:

• Failed to push gimlet-io/onechart-service:0.0.2-dev-PR-15.202106040734 and gimlet-io/onechart-service:0.0.2-dev-PR-15 (Source: ./)