Copyable: New utility interface for deep-copyable classes

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/config/Copyable.java

@@ -0,0 +1,9 @@
+package com.wireguard.config;
+
+/**
+ * Interface for classes that can perform a deep copy of their objects.
+ */
+
+public interface Copyable<T> {
+    T copy();
+}