Me/dpc 4280 patient entity converter bug (#2278)

## 🎫 Ticket

https://jira.cms.gov/browse/DPC-4280

## 🛠 Changes

Fixes bug in the `PatientEntity.toLocalDate()` method that caused it to
fail when given a date close to midnight.

## ℹ️ Context

If you passed a Date between 11pm and midnight to the
`PatientEntity.toLocalDate()` it would mistakenly return a `LocalDate`
for the next day. This was because in the conversion we were assuming
UTC time, and we are actually located in EST.

As for why the previous process failed, consider a `Date` of "1/1/2024
at 11:30pm EST". Converting that to UTC we get "1/2/2024 12:30am UTC".
Then converting it to a LocalDate, which has no concept of time zone, we
get "1/2/2024" when we were expecting "1/1/2024".

In the new version we use the system default time zone.

## 🧪 Validation

Created new test to verify results.

dpc-common/src/main/java/gov/cms/dpc/common/entities/PatientEntity.java

@@ -8,8 +8,7 @@
 import javax.validation.constraints.NotEmpty;
 import javax.validation.constraints.NotNull;
 import javax.validation.constraints.Pattern;
-import java.time.LocalDate;
-import java.time.ZoneOffset;
+import java.time.*;
 import java.util.Date;
 import java.util.List;
 import java.util.Objects;
@@ -144,14 +143,15 @@ public int hashCode() {
 
     @SuppressWarnings("JdkObsolete") // Date class is used by FHIR stu3 Patient model
     public static LocalDate toLocalDate(Date date) {
-        return date.toInstant()
-                .atZone(ZoneOffset.UTC)
-                .toLocalDate();
+        // LocalDateTime has no concept of time zone, so the best we can do is guess based on the system default.
+        // We should really avoid using it where possible.
+        return ZonedDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault())
+            .toLocalDate();
     }
 
     @SuppressWarnings("JdkObsolete") // Date class is used by FHIR stu3 Patient model
     public static Date fromLocalDate(LocalDate date) {
-        return Date.from(date.atStartOfDay().toInstant(ZoneOffset.UTC));
+        return Date.from(date.atStartOfDay(ZoneId.systemDefault()).toInstant());
     }
 
 

dpc-common/src/test/java/gov/cms/dpc/common/entities/PatientEntityTest.java

@@ -1,15 +1,12 @@
 package gov.cms.dpc.common.entities;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-import org.junit.jupiter.api.Test;
 import org.hl7.fhir.dstu3.model.Enumerations.AdministrativeGender;
-import java.time.LocalDate;
-import java.util.ArrayList;
-import java.util.Date;
-import java.util.List;
-import java.util.UUID;
+import org.junit.jupiter.api.Test;
+
+import java.time.*;
+import java.util.*;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 public class PatientEntityTest {
 
@@ -83,4 +80,19 @@ public void testLocalDateFunctions() {
 		assertNotNull(utilityDate);
 		assertEquals(localDate, convertedDate);
 	}
+
+	@Test
+	public void testToLocalDateHandlesTimeZoneChange() {
+		// A previous version of toLocalDate failed when converting a date/time close to midnight because it converted
+		// to UTC before getting the LocalDate.  Make sure that's no longer the case.
+
+		// 1/1/2024 11:55pm EST
+		Date testDate = new Calendar.Builder()
+			.setDate(2024, 0, 1)
+			.setTimeOfDay(23, 55, 0).build().getTime();
+
+		LocalDate resultLocalDate = PatientEntity.toLocalDate(testDate);
+
+		assertEquals(LocalDate.of(2024, 1, 1), resultLocalDate);
+	}
 }