Create skeleton code for fetching user's friends

backend-services/feed-service/app/models/User.scala

+package models
+
+import org.bson.types.ObjectId
+import scala.concurrent.Future
+import scala.concurrent.ExecutionContext.Implicits.global
+
+
+object User {
+    def getUserFriends(userId: ObjectId): Future[Seq[ObjectId]] = {
+        // TODO: Fetch user friends from Friend Service
+        val friends: Seq[ObjectId] = Seq(new ObjectId("641128f7e80bcd1ba39d04af"))
+        Future.successful(friends)
+    }
+}