Error validating app spec field "databases.version": "15" is not a supported database version

When trying to create my DO App Platform infrastructure with Terraform, I receive the following error:

error validating app spec field “databases.version”: “15” is not a supported database version

The database section of the app spec file is as follows:

database {
      name         = "${var.pg_edgedb_service_name}-${terraform.workspace}"
      engine       = "PG"
      version      = var.pg_edgedb_ver
      production   = terraform.workspace == "prod" ? true : false
      cluster_name = "edgedb-postgres-cluster-${terraform.workspace}"
    }

I receive the same error whether I pass in 15 , 14, or 13 for the version attribute. 12 seems to work–there is at least not an immediate field validation error. If I create a DB manually in the UI, versions 13, 14, and 15 are available for selection, and I can’t find any documentation to suggest that at least 13 shouldn’t work, so this has me pretty confused.

What versions are actually supported? Where can I find relevant documentation?