CloudFormation Stacks do not support lists as parameters.

[yannickvr]

Describe the bug
I'm trying to deploy a CF template using the customizations-config. My template expects a list as parameter, but the stack synthesis fails:

2024-03-12 13:07:28.249 | error | accelerator | Resolution error: Supplied properties not correct for "CfnStackSetProps"
  stackInstancesGroup: element 0: supplied properties not correct for "StackInstancesProperty"
    deploymentTargets: supplied properties not correct for "DeploymentTargetsProperty"
      organizationalUnitIds: "r-gqx8," should be a list.
/codebuild/output/src564/src/s3/00/source/packages/@aws-accelerator/accelerator/lib/accelerator.ts:58
    throw new Error('Synthesis failed');
    ^

To Reproduce

• Add a CloudFormation template to customizations-config.yaml as below:

homeRegion: &HOME_REGION eu-central-1
customizations:
  cloudFormationStackSets: []
  cloudFormationStacks: []
    - name: example
      description: example
      regions:
        - *HOME_REGION
      deploymentTargets:
        accounts:
          - Management
      runOrder: 1
      template: ./cfn-templates/example.yml
      terminationProtection: true  
      parameters:
        - name: ListParam
          value: 
            - r-gqx8  

Note: for value i tried:

• value: [ value ]
• value: "value"
• value: value,
• value: "value,"

All give either the same error, or error at build validation.

Parameter in CFN template:

Parameters:
  ListParam:
    Type: CommaDelimitedList

Expected behavior
Stack is deployed without errors

Please complete the following information about the solution:

• Version: 1.6.1
• Region: eu-central-1
• Was the solution modified from the version published on this repository? no
• If the answer to the previous question was yes, are the changes available on GitHub?
• Have you checked your service quotas for the services this solution uses? n/a
• Were there any errors in the CloudWatch Logs? Yes, see bug description

Screenshots
If applicable, add screenshots to help explain your problem (please DO NOT include sensitive information).

Additional context

[UnbiasedGoat]

I seem to be having this exact issue - I pass a value of "1111111111" to a TrustedAccounts CommaDelimitedList in a cdk bootstrap in the customizations config of lza and it fails validation with (CDKToolkit) failed: Error [ValidationError]: Template error: every Fn::Join object requires two parameters, (1) a string delimiter and (2) a list of strings to be joined or a function that returns a list of strings (such as Fn::GetAZs) to be joined.

Seems like it's not injecting the value correctly - have also many variations on the value but have yet to find a way to get it to work