refactor(code_push_protocol)!: remove appId from CreateChannelRequest (#862)

packages/shorebird_code_push_protocol/lib/src/messages/create_channel/create_channel_request.dart

@@ -3,12 +3,12 @@ import 'package:json_annotation/json_annotation.dart';
 part 'create_channel_request.g.dart';
 
 /// {@template create_channel_request}
-/// The request body for POST /api/v1/channels
+/// The request body for POST /api/v1/apps/<appId>/channels
 /// {@endtemplate}
 @JsonSerializable()
 class CreateChannelRequest {
   /// {@macro create_channel_request}
-  const CreateChannelRequest({required this.appId, required this.channel});
+  const CreateChannelRequest({required this.channel});
 
   /// Converts a Map<String, dynamic> to a [CreateChannelRequest]
   factory CreateChannelRequest.fromJson(Map<String, dynamic> json) =>
@@ -17,9 +17,6 @@ class CreateChannelRequest {
   /// Converts a [CreateChannelRequest] to a Map<String, dynamic>
   Map<String, dynamic> toJson() => _$CreateChannelRequestToJson(this);
 
-  /// The ID of the app.
-  final String appId;
-
   /// The channel name.
   final String channel;
 }

packages/shorebird_code_push_protocol/lib/src/messages/create_channel/create_channel_request.g.dart

@@ -15,17 +15,14 @@ CreateChannelRequest _$CreateChannelRequestFromJson(
       json,
       ($checkedConvert) {
         final val = CreateChannelRequest(
-          appId: $checkedConvert('app_id', (v) => v as String),
           channel: $checkedConvert('channel', (v) => v as String),
         );
         return val;
       },
-      fieldKeyMap: const {'appId': 'app_id'},
     );
 
 Map<String, dynamic> _$CreateChannelRequestToJson(
         CreateChannelRequest instance) =>
     <String, dynamic>{
-      'app_id': instance.appId,
       'channel': instance.channel,
     };

packages/shorebird_code_push_protocol/test/src/messages/create_channel/create_channel_request_test.dart

@@ -4,10 +4,7 @@ import 'package:test/test.dart';
 void main() {
   group(CreateChannelRequest, () {
     test('can be (de)serialized', () {
-      const request = CreateChannelRequest(
-        appId: 'my_app',
-        channel: 'my_channel',
-      );
+      const request = CreateChannelRequest(channel: 'my_channel');
       expect(
         CreateChannelRequest.fromJson(request.toJson()).toJson(),
         equals(request.toJson()),