charts/yeti Add OIDC authentication

[wajihyassine]

Description of the change

Adds a OIDC configuration option for the Yeti helm chart, to allow/deny users by oauth2.

To use, create oauth2 secret

    kubectl create secret generic oauth-secrets \
        --from-literal=client-id=<WEB_CLIENT_ID> \
        --from-literal=client-secret=<WEB_CLIENT_SECRET> \
        --from-literal=client-id-native=<NATIVE_CLIENT_ID>

Then install the chart

    helm install my-release osdfir-charts/yeti \
        --set ingress.enabled=true \
        --set ingress.host=<DOMAIN_NAME> \
        --set config.oidc.enabled=true \
        --set config.oidc.existingSecret=<OAUTH_SECRET_NAME> \

Checklist

• Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• Newly added variables are documented in the values.yaml
• Title of the pull request is descriptive