fix deprecation warning of Jackson ISO8601DateFormat

scm-webapp/src/test/java/sonia/scm/api/rest/ObjectMapperProviderTest.java

@@ -0,0 +1,24 @@
+package sonia.scm.api.rest;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import org.junit.jupiter.api.Test;
+
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ObjectMapperProviderTest {
+
+  private final ObjectMapperProvider provider = new ObjectMapperProvider();
+
+  @Test
+  void shouldFormatInstantAsISO8601() throws JsonProcessingException {
+    ZoneId zone = ZoneId.of("Europe/Berlin");
+    ZonedDateTime date = ZonedDateTime.of(2020, 2, 4, 15, 21, 42, 0, zone);
+
+    String value = provider.get().writeValueAsString(date.toInstant());
+    assertThat(value).isEqualTo("\"2020-02-04T14:21:42Z\"");
+  }
+
+}