api [nfc]: Rename StreamPostPolicy to ChannelPostPolicy

Fixes parts of zulip#631

Author: Khader-1

lib/api/model/model.dart

@@ -320,7 +320,7 @@ class Channel {
   final bool historyPublicToSubscribers;
   final int? messageRetentionDays;
   @JsonKey(name: 'stream_post_policy')
-  final StreamPostPolicy channelPostPolicy;
+  final ChannelPostPolicy channelPostPolicy;
   // final bool isAnnouncementOnly; // deprecated for `channelPostPolicy`; ignore
 
   // TODO(server-6): `canRemoveSubscribersGroupId` added in FL 142
@@ -359,19 +359,19 @@ class Channel {
   Map<String, dynamic> toJson() => _$ChannelToJson(this);
 }
 
-/// Policy for which users can post to the stream.
+/// Policy for which users can post to the channel.
 ///
 /// For docs, search for "stream_post_policy"
 /// in <https://zulip.com/api/get-stream-by-id>
 @JsonEnum(valueField: 'apiValue')
-enum StreamPostPolicy {
+enum ChannelPostPolicy {
   any(apiValue: 1),
   administrators(apiValue: 2),
   fullMembers(apiValue: 3),
   moderators(apiValue: 4),
   unknown(apiValue: null);
 
-  const StreamPostPolicy({
+  const ChannelPostPolicy({
     required this.apiValue,
   });
 

lib/api/model/model.g.dart

@@ -78,7 +78,7 @@ void main() {
       'is_web_public': false,
       'history_public_to_subscribers': true,
       'message_retention_days': null,
-      'stream_post_policy': StreamPostPolicy.any.apiValue,
+      'stream_post_policy': ChannelPostPolicy.any.apiValue,
       // 'can_remove_subscribers_group': null,
       'stream_weekly_traffic': null,
     });

test/api/model/model_test.dart

@@ -160,7 +160,7 @@ Channel stream({
   bool? isWebPublic,
   bool? historyPublicToSubscribers,
   int? messageRetentionDays,
-  StreamPostPolicy? channelPostPolicy,
+  ChannelPostPolicy? channelPostPolicy,
   int? canRemoveSubscribersGroup,
   int? channelWeeklyTraffic,
 }) {
@@ -175,7 +175,7 @@ Channel stream({
     isWebPublic: isWebPublic ?? false,
     historyPublicToSubscribers: historyPublicToSubscribers ?? true,
     messageRetentionDays: messageRetentionDays,
-    channelPostPolicy: channelPostPolicy ?? StreamPostPolicy.any,
+    channelPostPolicy: channelPostPolicy ?? ChannelPostPolicy.any,
     canRemoveSubscribersGroup: canRemoveSubscribersGroup ?? 123,
     channelWeeklyTraffic: channelWeeklyTraffic,
   );