fix: add zero check of day field in is_zeroed of IntervalNorm

Author: ZENOTME

src/interval_norm.rs

@@ -81,6 +81,7 @@ impl IntervalNorm {
     pub fn is_zeroed(&self) -> bool {
         self.years == 0
             && self.months == 0
+            && self.days == 0
             && self.hours == 0
             && self.minutes == 0
             && self.seconds == 0

src/pg_interval.rs

@@ -312,6 +312,13 @@ mod tests {
         assert_eq!(String::from("-01:10:15"), output);
     }
 
+    #[test]
+    fn test_postgres_19(){
+        let interval = Interval::new(0, 3, 0);
+        let output = interval.to_postgres();
+        assert_eq!(String::from("3 days"), output);
+    }
+
     #[test]
     fn test_sql_1() {
         let interval = Interval::new(12, 0, 0);