Error: only lowercase alphanumeric characters and hyphens allowed in "XXXXX"

╷
│ Error: only lowercase alphanumeric characters and hyphens allowed in "XXXX"
│
│   with module.db.aws_rds_cluster.this[0],
│   on .terraform/modules/path/tofile.tf line 56, in resource "aws_rds_cluster" "this":
│   56:     cluster_identifier = var.rds_cluster_identifier
│
╵

See also

• terraform plan: [ -refresh-only | -lock=false | -target | -var-file | will be created | --help], Terraform plan errors, Terraform plan examples, Terraform plan execution errors, (known after apply)