Set default securityContext for nextcloud-metrics

[Tuxprogrammer]

Sets best defaults for securityContext on nextcloud-metrics pod and container.

Pull Request

Description of the change

Add defaults to the deployment of nextcloud-metrics with selections for securityContext options on both pod and container.

Benefits

Clusters with higher security configurations can run nextcloud with metrics enabled.

Possible drawbacks

Unknown, if any.

Applicable issues

• fixes #

Additional information

Checklist

• [ ] DCO has been signed off on the commit.
• [ ] Chart version bumped in Chart.yaml according to semver.
• [ ] (optional) Variables are documented in the README.md

[Tuxprogrammer]

related to #356

[jessebot]

These defaults should be set in the values.yaml and then templated into the metrics/deployment.yaml. Could you please do that so that users can customize what gets applied? Also, please bump the helm chart version.