Add a check to ensure insertedMetaData is using an ID of 0

plugins/woocommerce/src/main/kotlin/org/wordpress/android/fluxc/model/metadata/UpdateMetadataRequest.kt

@@ -6,5 +6,12 @@ data class UpdateMetadataRequest(
     val insertedMetadata: List<WCMetaData> = emptyList(),
     val updatedMetadata: List<WCMetaData> = emptyList(),
     val deletedMetadata: List<WCMetaData> = emptyList(),
-)
-
+) {
+    init {
+        // The ID of inserted metadata is ignored, so to ensure that there is no data loss here,
+        // we require that all inserted metadata have an ID of 0.
+        require(insertedMetadata.all { it.id == 0L }) {
+            "Inserted metadata must have an ID of 0"
+        }
+    }
+}