[LLC, Persistence] Add doc comments

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

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

@@ -1,30 +1,43 @@
 import 'package:moor/moor.dart';
 import 'package:stream_chat_persistence/src/converter/map_converter.dart';
 
+/// Represents a [Channels] table in [MoorChatDatabase].
 @DataClassName('ChannelEntity')
 class Channels extends Table {
+  /// The id of this channel
   TextColumn get id => text()();
 
+  /// The type of this channel
   TextColumn get type => text()();
 
+  /// The cid of this channel
   TextColumn get cid => text()();
 
+  /// The channel configuration data
   TextColumn get config => text().map(MapConverter<Object>())();
 
+  /// True if this channel entity is frozen
   BoolColumn get frozen => boolean().withDefault(Constant(false))();
 
+  /// The date of the last message
   DateTimeColumn get lastMessageAt => dateTime().nullable()();
 
+  /// The date of channel creation
   DateTimeColumn get createdAt => dateTime().nullable()();
 
+  /// The date of the last channel update
   DateTimeColumn get updatedAt => dateTime().nullable()();
 
+  /// The date of channel deletion
   DateTimeColumn get deletedAt => dateTime().nullable()();
 
+  /// The count of this channel members
   IntColumn get memberCount => integer().nullable()();
 
+  /// The id of the user that created this channel
   TextColumn get createdById => text().nullable()();
 
+  /// Map of custom channel extraData
   TextColumn get extraData => text().nullable().map(MapConverter<Object>())();
 
   @override