invalid new value for .tags_all: new element "<tagname>" has appeared.

[roblevy]

When we tried to create a new RDS instance using this module, with a cluster_instance_tags block, we got the following message:

╷
│ Error: Provider produced inconsistent final plan
│ 
│ When expanding the plan for
│ module.insights_rds.aws_rds_cluster_instance.main[0] to include new values
│ learned so far during apply, provider "registry.terraform.io/hashicorp/aws"
│ produced an invalid new value for .tags_all: new element
│ "MasterCredentialsSecretManagerARN" has appeared.
│ 
│ This is a bug in the provider, which should be reported in the provider's
│ own issue tracker.
╵

This looks very much like an instance of this bug with the AWS Terraform provider itself.

I don't know if it's related but we were trying to set the tag value to be an ARN from a SecretsManager secret which was also being created IN THE SAME PR! Maybe that's why it's getting into difficulties:

  cluster_instance_tags = {
    MasterCredentialsSecretManagerARN = aws_secretsmanager_secret.insights_db_credentials.arn
  }