login.scala

case class LoginRequest(username: String, password: String)
case class UserDetails(username: String, hashedPassword: String)

def login(dbConn: DbConnection, req: Request): Try[Response] =
  for {
    reqJsonStr <- req.body
    reqJson <- json.parse(reqJsonStr)
    loginReq <- validateAndDecode[LoginRequest](reqJson)
    userDetails <- dbConn.findUser[UserDetails](dbConn, loginReq.username)
    _ <- doesPasswordMatch(userDetails.hashedPassword, loginReq.password)
    jwtToken <- jwt.generateToken()
  } yield Response(200, Map("token" -> jwtToken))