Summary
Add support for service.loadBalancerSourceRanges.
https://kubernetes.io/docs/reference/kubernetes-api/service-resources/service-v1/

Problem Statement
Recently we were trying to lock down our NodePorts to only allow our LoadBalancer access. That's when we noticed that this chart currently does not support service.loadBalancerSourceRanges.

Proposed Solution
Adding service.loadBalancerSourceRanges to the external service will give operators the chance to deny access to the Mailu NodePorts for the public and only accept traffic from the LoadBalancer.

Impact
The default value will be empty so the option will not affect existing workloads. Only when defined in values will it be rendered into the external Service definition.

Priority
Medium