fix: off by one error

Author: metacosm

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/ControllerUtils.java

@@ -48,7 +48,7 @@ public static String getDefaultResourceControllerName(String rcControllerClassNa
     // if the name is fully qualified, extract the simple class name
     final var lastDot = rcControllerClassName.lastIndexOf('.');
     if (lastDot > 0) {
-      rcControllerClassName = rcControllerClassName.substring(lastDot);
+      rcControllerClassName = rcControllerClassName.substring(lastDot + 1);
     }
     return rcControllerClassName.toLowerCase(Locale.ROOT);
   }

operator-framework-core/src/test/java/io/javaoperatorsdk/operator/ControllerUtilsTest.java

@@ -0,0 +1,17 @@
+package io.javaoperatorsdk.operator;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import io.javaoperatorsdk.operator.sample.simple.TestCustomResourceController;
+import org.junit.jupiter.api.Test;
+
+class ControllerUtilsTest {
+
+  @Test
+  void getDefaultResourceControllerName() {
+    assertEquals(
+        "testcustomresourcecontroller",
+        ControllerUtils.getDefaultResourceControllerName(
+            TestCustomResourceController.class.getCanonicalName()));
+  }
+}