cleanup: Remove unnecessary using from MongSchemaAdaptor

The recently added MongoCollectionStream dependend on these items. It
has been a while since I've looked at this branch, so I'm not sure what
happened, but the referenced members were no where to be found.

src/DataStreamSuite/DataStream/Primitives/MongoDB/MongoSchemaAdaptor.cs

@@ -1,7 +1,5 @@
 namespace Bts.DataStream;
 
-using BCG;
-
 using bts;
 
 using MongoDB.Bson;

src/DataStreamSuite/DataStreamCore/BlueData/BlueTableSchemaAdaptor.cs

@@ -9,7 +9,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 
-public class BlueTableSchemaAdaptor<T> {
+public class BlueTableSchemaAdaptor<T> : IMutableBlueRowFactory<T> {
    readonly string name;
    readonly List<ColumnAdaptor> columns = [];
    BlueTableSchema? schema;
@@ -60,7 +60,10 @@ public class BlueTableSchemaAdaptor<T> {
       columns.Add(new ColumnAdaptor(new(name, columns.Count, dataType), r => getValue(r)));
    }
 
-   public IBlueRow GetBlueRow(T item) {
+   public IBlueRow GetBlueRow(T item) =>
+      GetMutableBlueRow(item);
+
+   public MutableBlueRow GetMutableBlueRow(T item) {
       var mbr = new MutableBlueRow(Schema);
       foreach (var col in columns) {
          mbr.setValue(col.Info.colNo, col.GetValue(item));

src/DataStreamSuite/DataStreamCore/BlueData/IBlueRowFactory.cs

@@ -0,0 +1,9 @@
+#nullable enable
+namespace Bts.DataStream;
+
+using BCG;
+
+public interface IBlueRowFactory<T> {
+   IBlueTableSchema Schema { get; }
+   IBlueRow GetBlueRow(T item);
+}

src/DataStreamSuite/DataStreamCore/BlueData/IMutableBlueRowFactory.cs

@@ -0,0 +1,11 @@
+#nullable enable
+namespace Bts.DataStream;
+
+using BCG;
+
+public interface IMutableBlueRowFactory<T> : IBlueRowFactory<T> {
+   MutableBlueRow GetMutableBlueRow(T item);
+
+   IBlueRow IBlueRowFactory<T>.GetBlueRow(T item) =>
+      GetMutableBlueRow(item);
+}

src/DataStreamSuite/DataStreamCore/DataPacket.cs

@@ -313,4 +313,9 @@ namespace BCG
          return String.Format("DataPacket, schema {0} n {1} d {2} a {3}", schema.tableName, newRows.Count, deletedRows.Count, addedRows.Count);
       }
    }
+
+   public static class DataPacketExtensions {
+      public static bool HasChanges(this DataPacket dataPacket) =>
+         dataPacket.addedRows.Count > 0 || dataPacket.deletedRows.Count > 0;
+   }
 }