Change from MD5 to Checksum (Adler32) for json content dirty detection

ebean-core/src/test/java/io/ebeaninternal/server/util/ChecksumTest.java

@@ -0,0 +1,18 @@
+package io.ebeaninternal.server.util;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ChecksumTest {
+
+  @Test
+  public void checksum() {
+
+    final long val = Checksum.checksum("Hello world");
+    assertThat(val).isEqualTo(413860925L);
+
+    assertThat(Checksum.checksum("Hello world")).isEqualTo(val);
+    assertThat(Checksum.checksum("hello world")).isNotEqualTo(val);
+  }
+}