Add support for loadBalancerClass in LoadBalancer services

[raphaeltorquat0]

What this PR does

This adds a new configuration option load_balancer_class that allows users to specify which load balancer provider should handle the service when running multiple providers in the same cluster.

Fixes #2600

Changes

• Added load_balancer_class field to LoadBalancerConfiguration struct
• Added config mapping in importConfigurationFromCRD()
• Modified configureLoadBalanceService() to set spec.loadBalancerClass when configured
• Updated CRD schema with new field
• Updated default configuration manifest
• Added documentation

Example usage

apiVersion: acid.zalan.do/v1
kind: OperatorConfiguration
metadata:
  name: postgres-operator
configuration:
  load_balancer:
    enable_master_load_balancer: true
    load_balancer_class: "service.k8s.aws/nlb"

Type of change

• New feature (non-breaking change which adds functionality)

Note: parts of this implementation were developed with AI assistance.

[raphaeltorquat0]

Hi! Could a maintainer please add the appropriate label to this PR? I believe minor would be suitable as this adds a new non-breaking feature. Thank you!

[FxKu]

To use NLBs we usually do it via serviceAnnotations - begs the question if we really need another option. Plus, how would you get two LBs? Is the old LB with other class not dropped when you switch the class?

  serviceAnnotations:
    service.beta.kubernetes.io/aws-load-balancer-type: nlb
    service.beta.kubernetes.io/aws-load-balancer-internal: "true"