addAuthentication uses SttpRequest but zio env is optional

[gurghet]

tamer/example/src/main/scala/tamer/rest/RESTCustomAuth.scala

Line 21 in 8c8c40f

override def addAuthentication(request: SttpRequest, bearerToken: Option[String]): SttpRequest = request.auth.bearer(bearerToken.getOrElse(""))

This can result in code like this for custom auth:

val authentication: Authentication[Any] = new Authentication[Any] {
    override def addAuthentication(request: SttpRequest, supplementalSecret: Option[String]): SttpRequest =
    // ...
}

A suggestion is to make the type parameter -R <: SttpClient or to make authentication independent from any particular client.