add fields param in toxcontent() for doc level query (#549) (#555)

(cherry picked from commit f290fec)

Signed-off-by: Surya Sashank Nistala <snistala@amazon.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

src/main/kotlin/org/opensearch/commons/alerting/model/DocLevelQuery.kt

@@ -59,6 +59,7 @@ data class DocLevelQuery(
         builder.startObject()
             .field(QUERY_ID_FIELD, id)
             .field(NAME_FIELD, name)
+            .field(FIELDS_FIELD, fields.toTypedArray())
             .field(QUERY_FIELD, query)
             .field(TAGS_FIELD, tags.toTypedArray())
             .endObject()

src/test/kotlin/org/opensearch/commons/alerting/model/XContentTests.kt

@@ -417,6 +417,18 @@ class XContentTests {
         )
     }
 
+    @Test
+    fun `test doc level query toXcontent`() {
+        val dlq = DocLevelQuery("id", "name", listOf("f1", "f2"), "query", listOf("t1", "t2"))
+        val dlqString = dlq.toXContent(builder(), ToXContent.EMPTY_PARAMS).string()
+        val parsedDlq = DocLevelQuery.parse(parser(dlqString))
+        Assertions.assertEquals(
+            dlq,
+            parsedDlq,
+            "Round tripping Doc level query doesn't work"
+        )
+    }
+
     @Test
     fun `test alert parsing`() {
         val alert = randomAlert()