ES DA failing validation with Error: Invalid template interpolation value

[ocofaigh]

Seeing this error even when existing_secrets_manager_instance_crn is set to null:

 2024/09/25 11:23:28 Terraform plan | Error: Invalid template interpolation value
 2024/09/25 11:23:28 Terraform plan | 
 2024/09/25 11:23:28 Terraform plan |   on main.tf line 175, in locals:
 2024/09/25 11:23:28 Terraform plan |  175:     secret_group_name     = var.prefix != null ? "${var.prefix}-${var.admin_pass_sm_secret_group}" : var.admin_pass_sm_secret_group
 2024/09/25 11:23:28 Terraform plan |     ├────────────────
 2024/09/25 11:23:28 Terraform plan |     │ var.admin_pass_sm_secret_group is null
 2024/09/25 11:23:28 Terraform plan | 
 2024/09/25 11:23:28 Terraform plan | The expression result is null. Cannot include a null value in a string
 2024/09/25 11:23:28 Terraform plan | template.
 2024/09/25 11:23:28 Terraform plan | 
 2024/09/25 11:23:28 Terraform plan | Error: Invalid template interpolation value
 2024/09/25 11:23:28 Terraform plan | 
 2024/09/25 11:23:28 Terraform plan |   on main.tf line 178, in locals:
 2024/09/25 11:23:28 Terraform plan |  178:       secret_name             = var.prefix != null ? "${var.prefix}-${var.admin_pass_sm_secret_name}" : var.admin_pass_sm_secret_name
 2024/09/25 11:23:28 Terraform plan |     ├────────────────
 2024/09/25 11:23:28 Terraform plan |     │ var.admin_pass_sm_secret_name is null
 2024/09/25 11:23:28 Terraform plan | 
 2024/09/25 11:23:28 Terraform plan | The expression result is null. Cannot include a null value in a string

[ocofaigh]

Fixed in #298