Add unit tests for models and services

- Implemented unit tests for the Package model, covering methods such as generateId, findById, findByName, and version management.
- Created unit tests for the Repository model, including repository creation, name validation, and retrieval methods.
- Added tests for the Session model, focusing on session creation, validation, and invalidation.
- Developed unit tests for the User model, ensuring user creation, password hashing, and retrieval methods function correctly.
- Implemented AuthService tests, validating login, token refresh, and session management.
- Added TokenService tests, covering token creation, validation, and revocation processes.

test/fixtures/maven/com/stacktest/demo-artifact/pom.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
+                             http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.stacktest</groupId>
+    <artifactId>demo-artifact</artifactId>
+    <version>1.0.0</version>
+    <packaging>jar</packaging>
+    <name>Stack.Gallery Demo Artifact</name>
+    <description>Demo Maven artifact for e2e tests</description>
+    <url>https://github.com/stack-gallery/demo-artifact</url>
+
+    <licenses>
+        <license>
+            <name>MIT License</name>
+            <url>https://opensource.org/licenses/MIT</url>
+        </license>
+    </licenses>
+
+    <developers>
+        <developer>
+            <name>Stack.Gallery Test</name>
+            <email>test@stack.gallery</email>
+        </developer>
+    </developers>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+</project>

test/fixtures/maven/com/stacktest/demo-artifact/src/main/java/com/stacktest/Demo.java

@@ -0,0 +1,19 @@
+package com.stacktest;
+
+/**
+ * Demo class for Stack.Gallery Registry e2e tests.
+ */
+public class Demo {
+    /**
+     * Greet the given name.
+     * @param name The name to greet
+     * @return A greeting message
+     */
+    public static String greet(String name) {
+        return "Hello, " + name + "!";
+    }
+
+    public static void main(String[] args) {
+        System.out.println(greet("World"));
+    }
+}