Add custom QZ Tray fork with pairing key authentication

- Custom fork of QZ Tray 2.2.x with certificate validation bypassed
- Implemented pairing key (HMAC) authentication as replacement
- Modified files: PrintSocketClient.java (certificate check disabled)
- New files: PairingAuth.java, PairingConfigDialog.java
- Excluded build artifacts (out/, lib/javafx*) from repository
- Library JARs included for dependency management

tray/src/qz/common/CachedObject.java

@@ -0,0 +1,97 @@
+package qz.common;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Supplier;
+
+/**
+ * A generic class that encapsulates an object for caching. The cached object
+ * will be refreshed automatically when accessed after its lifespan has expired.
+ *
+ * @param <T> The type of object to be cached.
+ */
+public class CachedObject<T> {
+    public static final long DEFAULT_LIFESPAN = 5000; // in milliseconds
+    T lastObject;
+    Supplier<T> supplier;
+    private long timestamp;
+    private long lifespan;
+
+    /**
+     * Creates a new CachedObject with a default lifespan of 5000 milliseconds
+     *
+     * @param supplier The function to pull new values from
+     */
+    public CachedObject(Supplier<T> supplier) {
+        this(supplier, DEFAULT_LIFESPAN);
+    }
+
+    /**
+     * Creates a new CachedObject
+     *
+     * @param supplier The function to pull new values from
+     * @param lifespan The lifespan of the cached object in milliseconds
+     */
+    public CachedObject(Supplier<T> supplier, long lifespan) {
+        this.supplier = supplier;
+        setLifespan(lifespan);
+        timestamp = Long.MIN_VALUE;  // System.nanoTime() can be negative, MIN_VALUE guarantees a first-run.
+    }
+
+    /**
+     * Registers a new supplier for the CachedObject
+     *
+     * @param supplier The function to pull new values from
+     */
+    @SuppressWarnings("unused")
+    public void registerSupplier(Supplier<T> supplier) {
+        this.supplier = supplier;
+    }
+
+    /**
+     * Sets the lifespan of the cached object
+     *
+     * @param milliseconds The lifespan of the cached object in milliseconds
+     */
+    public void setLifespan(long milliseconds) {
+        lifespan = Math.max(0, milliseconds); // prevent overflow
+    }
+
+    /**
+     * Retrieves the cached object.
+     * If the cached object's lifespan has expired, it gets refreshed before being returned.
+     *
+     * @return The cached object
+     */
+    public T get() {
+        return get(false);
+    }
+
+    /**
+     * Retrieves the cached object.
+     * If the cached object's lifespan is expired or forceRefresh is true, it gets refreshed before being returned.
+     *
+     * @param forceRefresh If true, the cached object will be refreshed before being returned regardless of its lifespan
+     * @return The cached object
+     */
+    public T get(boolean forceRefresh) {
+        long now = TimeUnit.NANOSECONDS.toMillis(System.nanoTime());
+        // check lifespan
+        if (forceRefresh || (timestamp + lifespan <= now)) {
+            timestamp = now;
+            lastObject = supplier.get();
+        }
+        return lastObject;
+    }
+
+    // Test
+    public static void main(String ... args) throws InterruptedException {
+        final AtomicInteger testInt = new AtomicInteger(0);
+
+        CachedObject<Integer> cachedString = new CachedObject<>(testInt::incrementAndGet);
+        for(int i = 0; i < 100; i++) {
+            Thread.sleep(1500);
+            System.out.println(cachedString.get());
+        }
+    }
+}