Add IDP service chart

[mirekys]

Adds a deployment Chart of an OpenID Connect Identity Provider service, compatible with CS3 APIs, based on OCIS IDP implementation. This service is required to enable users to log in to 3rdparty services using their ScienceMesh accounts (sciencemesh/sciencemesh#176).

Contributing a Chart / update to an existing Chart

• Run helm lint on the chart dir.
• (Update) Bump the Chart.yaml version before merging, to release it as a new version.
• (Update) If the PR includes new configurable parameters in the chart's values.yaml. Add documentation in the appropiate README.

[mirekys]

The GH action helm/chart-testing-action version used for linting seems to be quite outdated (Jul 2020), using old helm version. The randBytes function used by the chart was introduced in helm at Dec 2020 https://github.com/Masterminds/sprig/blob/master/CHANGELOG.md#release-320-2020-12-14, would it be OK to update the GH action in workflow? @SamuAlfageme