feat: Update gwlb deregistration behavior

[ntwrkguru]

Description

The target group behavior upon deregistration is not currently exposed and only follows the provider defaults. This PR adds the possibility to manage this behavior via our module.

Motivation and Context

Client requested the ability to manage this behavior.

How Has This Been Tested?

Local testing

Screenshots (if appropriate)

Types of changes

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

Checklist

• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
• All new and existing tests passed.

[sebastianczech]

After merging main in commit 8c1e3fe (https://github.com/PaloAltoNetworks/terraform-aws-swfw-modules/pull/73/commits) , all your changes were overwritten. Are you able to restore what you had in 8bb0664 , please ?

Regarding validations introduced in this commit - I'm not sure if this is good approach as currently module show work with Terraform 1.0 or newer:

https://github.com/PaloAltoNetworks/terraform-aws-swfw-modules/blob/main/modules/gwlb/versions.tf

Referencing to other variables in validations was introduced in Terraform 1.9:

Previously, the condition block of an input validation could refer only to the variable itself. With Terraform 1.9, conditions can now refer to other input variables and even to other objects, such as data sources and local values, greatly expanding the kinds of scenarios that authors can validate. (source: https://www.hashicorp.com/blog/terraform-1-9-enhances-input-variable-validations)

[migara]

@ntwrkguru can you please restore your commits in here as @sebastianczech suggested?

Also can you please consolidate the two variables in a single one with two keys and change the validation logic to something like this?

[sebastianczech]

In variables.tf variable rebalance_flows is defined as bool.
In Terraform registry https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/lb_target_group for on_deregistration and on_unhealthy we have 2 possible values, which are string, not bool:

• rebalance
• no_rebalance

Does it work for you with bool values?