Dependency duplication when creating a fat jar for playframework with play-ws

Question

I noticed that when trying to build fat jara for playframework 2.7 with play-ws (sbt assembly), dependency duplications occur. I get a lot of errors related to javax.activation-api and shaded-asynchttpclient e.g.

[error] deduplicate: different file contents found in the following:
[error] /home/user/.cache/coursier/v1/https/repo1.maven.org/maven2/javax/activation/javax.activation-api/1.2.0/javax.activation-api-1.2.0.jar:javax/activation/UnsupportedDataTypeException.class
[error] /home/user/.cache/coursier/v1/https/repo1.maven.org/maven2/com/typesafe/play/shaded-asynchttpclient/2.0.6/shaded-asynchttpclient-2.0.6.jar:javax/activation/UnsupportedDataTypeException.class

The problem turns out to be the play-ws without which sbt assembly is carried out correctly. The only place in my code where I explicitly use javax is dependency injection. Using guice instead gives the same result. Here is my build.sbt (which is based on https://www.playframework.com/documentation/2.7.x/Deploying)

name := "My-App"
version := "1.0"
scalaVersion := "2.11.12"

lazy val root = (project in file(".")).enablePlugins(PlayScala)
scalaSource in ThisScope := baseDirectory.value
mainClass in assembly := Some("play.core.server.ProdServerStart")
fullClasspath in assembly += Attributed.blank(PlayKeys.playPackageAssets.value)

libraryDependencies ++= Seq(
  ws,
  specs2 % Test,
  "com.typesafe.play" %% "play-json" % "2.7.4",
  "com.typesafe.play" %% "play-slick" % "4.0.2",
  "com.typesafe.play" %% "play-slick-evolutions" % "4.0.2",
  "com.typesafe" % "config" % "1.4.0",
  "org.mindrot" % "jbcrypt" % "0.4",
  "mysql" % "mysql-connector-java" % "8.0.17",
  "org.mindrot" % "jbcrypt" % "0.4",
  "com.iheart" %% "ficus" % "1.4.7",
  "com.typesafe.scala-logging" % "scala-logging_2.11" % "3.9.0"
)

assemblyMergeStrategy in assembly := {
  case manifest if manifest.contains("MANIFEST.MF") =>
    // We don't need manifest files since sbt-assembly will create
    // one with the given settings
    MergeStrategy.discard
  case referenceOverrides if referenceOverrides.contains("reference-overrides.conf") =>
    // Keep the content for all reference-overrides.conf files
    MergeStrategy.concat
  case x =>
    // For all the other files, use the default sbt-assembly merge strategy
    val oldStrategy = (assemblyMergeStrategy in assembly).value
    oldStrategy(x)
}