Enable rootless settings for nginx containers by default

[BorisPolonsky]

Description

This release enables podSecurityContext and containerSecurityContext for the proxy component by default, running nginx as a non-root user (UID 101).
Close #359

Action required for existing deployments

If you have proxy.log.persistence.enabled: true with an existing PVC (nginx-logs-disk):

• update the volume ownership before upgrading, or
• as alternative, disable security contexts for backward compatibility by setting:

proxy:
  podSecurityContext:
    enabled: false
  containerSecurityContext:
    enabled: false