Introduce some UUID utilities for eventual auth support.

src/test/java/com/velocitypowered/proxy/util/UuidUtilsTest.java

@@ -0,0 +1,26 @@
+package com.velocitypowered.proxy.util;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.UUID;
+
+import static org.junit.Assert.*;
+
+public class UuidUtilsTest {
+    private static final UUID VALID_UUID = UUID.fromString("6b501978-d3be-4f33-bcf6-6e7808f37a0d");
+    private static final String VALID_MOJANG_UUID = "6b501978d3be4f33bcf66e7808f37a0d";
+
+    private static final UUID TEST_OFFLINE_PLAYER_UUID = UUID.fromString("708f6260-183d-3912-bbde-5e279a5e739a");
+    private static final String TEST_OFFLINE_PLAYER = "tuxed";
+
+    @Test
+    public void fromMojang() {
+        Assert.assertEquals("UUIDs do not match", VALID_UUID, UuidUtils.fromMojang(VALID_MOJANG_UUID));
+    }
+
+    @Test
+    public void generateOfflinePlayerUuid() {
+        Assert.assertEquals("UUIDs do not match", TEST_OFFLINE_PLAYER_UUID, UuidUtils.generateOfflinePlayerUuid(TEST_OFFLINE_PLAYER));
+    }
+}