fix: Fix nil pointer in Cluster

[lantoli]

Proposed changes

Fix nil pointer in Cluster. Cluster creation would fail for cluster configs without AdvancedSettings.
Fix regression introduced in #1344.
Issue was not caught in E2E or contract tests because they use AdvancedSettings.

Jira ticket: CLOUDP-321622

Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as
  expected)
• This change requires a documentation update
• If changes include removal or addition of 3rd party GitHub actions, I updated our internal document. Reach out to the APIx Integration slack channel to get access to the internal document.

Manual QA performed:

• cfn invoke for each of CRUDL/cfn test
• Updated resource in example
• Published to AWS private registry
• Used the template in example to create and update a stack in AWS
• Deleted stack to ensure resources are deleted
• Created multiple resources in same stack
• Validated in Atlas UI
• Included screenshots

Required Checklist:

• I have signed the MongoDB CLA
• I have added tests that prove my fix is effective or that my feature works
• I have checked that this change does not generate any credentials and that they are NOT accidentally logged anywhere.
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code
• For CFN Resources: I have released by changes in the private registry and proved by change
  works in Atlas

Further comments

[Copilot]

Pull Request Overview

This PR aims to fix a nil pointer deference issue during Cluster creation by adding appropriate nil checks.

• Corrects a mistaken nil check on the label’s Value field.
• Adds a nil check for AdvancedSettings to prevent nil pointer issues.
• Ensures proper pointer handling for CustomOpensslCipherConfigTls12 in the advanced configuration.

Comments suppressed due to low confidence (2)

cfn-resources/cluster/cmd/resource/mappings.go:204

• Changing the check from labels[i].Key to labels[i].Value correctly prevents a nil pointer dereference when accessing the Value field. Confirm that similar nil checks are applied consistently in related logic if necessary.

if labels[i].Value != nil {

cfn-resources/cluster/cmd/resource/mappings.go:619

• The added nil check for processArgs.CustomOpensslCipherConfigTls12 ensures safe pointer handling. Please verify that pointer assignments follow the same pattern consistently across similar configurations.

if processArgs.CustomOpensslCipherConfigTls12 != nil {

[Copilot]

Adding the nil check for currentModel.AdvancedSettings prevents a potential nil pointer deference during cluster creation. This approach improves the robustness of the cluster setup.

[oarbusi]

Thank you!!

[AgustinBettati]

Should we add a contract test which does not define AdvancedSettings?

[lantoli]

ticket created: CLOUDP-321624