fix: re-add AbstractEvent for backwards compatibility

Author: metacosm

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/AbstractEvent.java

@@ -0,0 +1,20 @@
+package io.javaoperatorsdk.operator.processing.event;
+
+import io.fabric8.kubernetes.client.CustomResource;
+import java.util.function.Predicate;
+
+/**
+ * @deprecated use {@link DefaultEvent} instead
+ */
+@Deprecated
+public class AbstractEvent extends DefaultEvent {
+
+  public AbstractEvent(String relatedCustomResourceUid, EventSource eventSource) {
+    super(relatedCustomResourceUid, eventSource);
+  }
+
+  public AbstractEvent(
+      Predicate<CustomResource> customResourcesSelector, EventSource eventSource) {
+    super(customResourcesSelector, eventSource);
+  }
+}