feat!: implemented multigame support (#34)

Reviewed-on: #34
Co-authored-by: Janis <janis.e.20@gmx.de>
Co-committed-by: Janis <janis.e.20@gmx.de>

knockoutwhistweb/app/logic/user/UserManager.scala

@@ -0,0 +1,16 @@
+package logic.user
+
+import com.google.inject.ImplementedBy
+import logic.user.impl.StubUserManager
+import model.users.User
+
+@ImplementedBy(classOf[StubUserManager])
+trait UserManager {
+
+  def addUser(name: String, password: String): Boolean
+  def authenticate(name: String, password: String): Option[User]
+  def userExists(name: String): Option[User]
+  def userExistsById(id: Long): Option[User]
+  def removeUser(name: String): Boolean
+
+}