HHH-13048 Allow for parallel processing of entity enhancements via ByteBuddy

hibernate-core/src/main/java/org/hibernate/bytecode/enhance/internal/bytebuddy/EnhancerImpl.java

@@ -96,7 +96,7 @@ public class EnhancerImpl implements Enhancer {
 	 * @throws EnhancementException Indicates a problem performing the enhancement
 	 */
 	@Override
-	public synchronized byte[] enhance(String className, byte[] originalBytes) throws EnhancementException {
+	public byte[] enhance(String className, byte[] originalBytes) throws EnhancementException {
 		//Classpool#describe does not accept '/' in the description name as it expects a class name. See HHH-12545
 		final String safeClassName = className.replace( '/', '.' );
 		try {

hibernate-core/src/main/java/org/hibernate/bytecode/enhance/spi/Enhancer.java

@@ -18,6 +18,10 @@ public interface Enhancer {
 	/**
 	 * Performs the enhancement.
 	 *
+	 * It is possible to invoke this method concurrently, but when doing so make sure
+	 * no two enhancement tasks are invoked on the same class in parallel: the
+	 * Enhancer implementations are not required to guard against this.
+	 *
 	 * @param className The name of the class whose bytecode is being enhanced.
 	 * @param originalBytes The class's original (pre-enhancement) byte code
 	 *