Add: User to link network to domain

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/domain/user/User.java

@@ -0,0 +1,28 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.domain.user;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.network.sessions.SessionId;
+import java.util.Optional;
+
+public class User {
+    private final UserId id;
+    private final String name;
+    private SessionId sessionId;
+
+    public User(UserId id, String name, SessionId sessionId) {
+        this.id = id;
+        this.name = name;
+        this.sessionId = sessionId;
+    }
+
+    public UserId getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Optional<SessionId> getSessionId() {
+        return Optional.ofNullable(sessionId);
+    }
+}