feature: Metadata Mapping pattern (#1932)

* metadata-mapping

* Update README.md

* add class diagram

* update README.md

* fix identation

* Update pom.xml

* fix indentation

* fix ci

* remove e.printstack

* fix ci

* update class diagram

* fix ci

* fix ci

* fix sc

* fix smells

* Update DatabaseUtil.java

* fix coverage

* Update DatabaseUtil.java

* Update DatabaseUtil.java

* Update DatabaseUtil.java

* Update metadata-mapping/README.md

Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>

* fix review

* fix review

* Update App.java

* Update App.java

* fix review

Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>

metadata-mapping/src/test/java/com/iluwatar/metamapping/AppTest.java

@@ -0,0 +1,20 @@
+package com.iluwatar.metamapping;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+/**
+ * Tests that metadata mapping example runs without errors.
+ */
+class AppTest {
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+  @Test
+  void shouldExecuteMetaMappingWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
+  }
+}