[StreamChatPersistence] Add initial implementation

Signed-off-by: Sahil Kumar <[email protected]>

packages/stream_chat_persistence/lib/src/entity/reads.dart

@@ -0,0 +1,19 @@
+import 'package:moor/moor.dart';
+
+@DataClassName('ReadEntity')
+class Reads extends Table {
+  DateTimeColumn get lastRead => dateTime()();
+
+  TextColumn get userId => text()();
+
+  TextColumn get channelCid =>
+      text().customConstraint('REFERENCES channels(cid) ON DELETE CASCADE')();
+
+  IntColumn get unreadMessages => integer().nullable()();
+
+  @override
+  Set<Column> get primaryKey => {
+        userId,
+        channelCid,
+      };
+}