Configure SonarCloud

Since latest update sonar cloud gets very angry with our code. We need to configure it so it reports only issues that we consider issues.

To do so one needs to adjust `sonar-project.properties` (https://github.com/owncloud/ocis/blob/master/sonar-project.properties) and `golangci.yaml` (https://github.com/owncloud/ocis/blob/master/.golangci.yml)

See also main branch overview for current issues: https://sonarcloud.io/summary/overall?id=owncloud_ocis

Goal of this ticket: Configure sonarcloud to
- not show `package-comment` errors
- only show `cyclomatic-complexity` errors > 35
- share knowledge with other developers so they can adjust sonarcloud when they run into other issues.
- reenable depguard linter with a sane configuration