Add Timestamp.ServerDelete and relatives tests.

Author: corrado4eyes

firebase-firestore/src/commonMain/kotlin/dev/gitlive/firebase/firestore/FirebaseTimestamp.kt

@@ -3,9 +3,11 @@ package dev.gitlive.firebase.firestore
 sealed class FirebaseTimestamp {
     data class Value(val value: Timestamp) : FirebaseTimestamp()
     object ServerValue : FirebaseTimestamp()
+    object ServerDelete : FirebaseTimestamp()
 }
 
 val FirebaseTimestamp.timestamp: Timestamp? get() = when (this) {
     is FirebaseTimestamp.Value -> value
-    is FirebaseTimestamp.ServerValue -> null
+    is FirebaseTimestamp.ServerValue,
+    is FirebaseTimestamp.ServerDelete -> null
 }

firebase-firestore/src/commonMain/kotlin/dev/gitlive/firebase/firestore/TimestampSerializer.kt

@@ -39,6 +39,9 @@ abstract class AbstractTimestampSerializer<T> : KSerializer<T> {
             is FirebaseTimestamp.ServerValue -> {
                 objectEncoder.encodeObject(descriptor, 0, FieldValue.serverTimestamp())
             }
+            is FirebaseTimestamp.ServerDelete -> {
+                objectEncoder.encodeObject(descriptor, 0, FieldValue.delete)
+            }
         }
         objectEncoder.endStructure(descriptor)
     }

firebase-firestore/src/commonTest/kotlin/dev/gitlive/firebase/firestore/TimestampTests.kt

@@ -62,4 +62,30 @@ class TimestampTests {
         assertEquals("uid123", decoded.uid)
         assertEquals(null, decoded.updatedAt)
     }
+
+    @Test
+    fun decodeDeletedTimestampObject() = runTest {
+        val timestamp = timestampWith(123, 345)
+        val obj = mapOf(
+            "uid" to "uid123",
+            "createdAt" to timestampNow(),
+            "updatedAt" to FieldValue.delete,
+            "deletedAt" to FirebaseTimestamp.ServerDelete
+        )
+        val decoded: TestData = decode(obj)
+
+        assertEquals("uid123", decoded.uid)
+        assertEquals(null, decoded.updatedAt)
+        assertEquals(null, decoded.deletedAt)
+    }
+
+    @Test
+    fun encodeDeletedTimestampObject() = runTest {
+        val timestamp = FieldValue.delete
+        val item = TestData("uid123", timestamp, null, FirebaseTimestamp.ServerDelete)
+        val encoded = encode(item, shouldEncodeElementDefault = false) as Map<String, Any?>
+        assertEquals("uid123", encoded["uid"])
+        assertEquals(timestamp, encoded["createdAt"])
+        assertEquals(FieldValue.delete, encoded["deletedAt"])
+    }
 }