Fix: Treat login id as string (UUID) in LoginResult

Change LoginResult.id from int to String and add Javadoc explaining the server returns a UUID.
BREAKING CHANGE: LoginResult.getId() now returns String (UUID).

src/main/java/ch/unibas/dmi/dbis/cs108/casono/client/network/LoginResult.java

@@ -0,0 +1,38 @@
+package ch.unibas.dmi.dbis.cs108.casono.client.network;
+
+/**
+ * Result of a successful login request.
+ *
+ * <p>Holds the username assigned by the server and the server-side id as a string (UUID). The
+ * client previously attempted to parse the id as an integer which failed when the server returned a
+ * UUID; this class therefore stores the id as a {@link String}.
+ */
+public class LoginResult {
+    private final String username;
+    private final String id;
+
+    /**
+     * Create a login result.
+     *
+     * @param username the assigned username
+     * @param id the assigned id (UUID string) returned by the server
+     */
+    public LoginResult(String username, String id) {
+        this.username = username;
+        this.id = id;
+    }
+
+    /**
+     * @return the assigned username
+     */
+    public String getUsername() {
+        return username;
+    }
+
+    /**
+     * @return the assigned id as returned by the server (UUID string)
+     */
+    public String getId() {
+        return id;
+    }
+}