fix: support 'localtime' as a timezone (#625)

Author: olavloite

src/main/java/com/google/cloud/spanner/pgadapter/session/PGSetting.java

@@ -458,6 +458,9 @@ static String convertToValidZoneId(String value) {
  if ("utc".equalsIgnoreCase(value)) {
  return "UTC";
  }
+ if ("localtime".equalsIgnoreCase(value)) {
+ return ZoneId.systemDefault().getId();
+ }
  for (String zoneId : ZoneId.getAvailableZoneIds()) {
  if (zoneId.equalsIgnoreCase(value)) {
  return zoneId;

src/test/java/com/google/cloud/spanner/pgadapter/JdbcMockServerTest.java

@@ -2956,6 +2956,16 @@ public void testSetTimeZoneToServerDefault() throws SQLException {
  }
  }
 
+ @Test
+ public void testSetTimeZoneToLocaltime() throws SQLException {
+ try (Connection connection = DriverManager.getConnection(createUrl())) {
+ connection.createStatement().execute("set time zone 'atlantic/jan_mayen'");
+ verifySettingValue(connection, "timezone", "Atlantic/Jan_Mayen");
+ connection.createStatement().execute("set time zone localtime");
+ verifySettingValue(connection, "timezone", TimeZone.getDefault().getID());
+ }
+ }
+
  @Test
  public void testSetTimeZoneToDefault() throws SQLException {
  try (Connection connection =