normalize years and months part in coverting Avro interval to ISO8601 string

Author: Sagar Agarwal

v2/spanner-common/src/main/java/com/google/cloud/teleport/v2/spanner/migrations/avro/GenericRecordTypeConvertor.java

@@ -708,7 +708,9 @@ static String handleRecordFieldType(String fieldName, GenericRecord element, Sch
           Period.ZERO
               .plusYears(((Number) getOrDefault(element, "years", 0L)).longValue())
               .plusMonths(((Number) getOrDefault(element, "months", 0L)).longValue())
-              .plusDays(((Number) getOrDefault(element, "days", 0L)).longValue());
+              .plusDays(((Number) getOrDefault(element, "days", 0L)).longValue())
+              .normalized(); // Normalize years and months
+
       /*
        * Convert the period to a ISO-8601 period formatted String, such as P6Y3M1D.
        * A zero period will be represented as zero days, 'P0D'.

v2/spanner-common/src/test/java/com/google/cloud/teleport/v2/spanner/migrations/avro/GenericRecordTypeConvertorTest.java

@@ -712,10 +712,10 @@ public void testIntervalNanos() {
     result =
         GenericRecordTypeConvertor.handleRecordFieldType(
             "interval_nanos_column",
-            AvroTestingHelper.createIntervalNanosRecord(1000L, 1000L, 3890L, 25L, 331L, 12L, 9L),
+            AvroTestingHelper.createIntervalNanosRecord(1000L, 1000L, 3890L, 25L, 331L, 3672L, 9L),
             AvroTestingHelper.INTERVAL_NANOS_SCHEMA);
     assertEquals(
-        "Test #1 interval nano conversion:", "P1000Y1000M3890DT30H31M12.000000009S", result);
+        "Test #1 interval nano conversion:", "P1083Y4M3890DT31H32M12.000000009S", result);
 
     /* Test with any field set as null gets treated as 0. */
     result =
@@ -736,7 +736,7 @@ public void testIntervalNanos() {
             AvroTestingHelper.INTERVAL_NANOS_SCHEMA);
     assertEquals(
         "Test #3 interval nano conversion with negative months:",
-        "P1000Y-1000M3890DT25H31M12.000000009S",
+        "P916Y8M3890DT25H31M12.000000009S",
         result);
 
     /* Test that negative nanos subtract from the fractional seconds, for example 12 Seconds -1 Nanos becomes 11.999999991s. */