MetadataAsWritter.scala

import cats.data.Writer
import cats.syntax.writer._
import cats.instances.all._

type Metadata[Meta, T] = Writer[Meta, T]

object syntax {
  implicit def metadataAs[Meta, T](m:  Metadata[Meta, T]): T = m.run._2
  implicit class MetadataExt[T](x: T) {
    def withMetadata[Meta](m: Meta): Metadata[Meta, T] = Writer.apply(m, x)
  }
}

case class AnEntity(name: String)

import syntax._
val a = AnEntity("hello")
val aWithMeta = a.withMetadata(System.currentTimeMillis)
println(aWithMeta.name)