Add postingRestrictedToMods to channels AP objects

See https://github.com/LemmyNet/lemmy/issues/3837

packages/models/src/activitypub/activitypub-actor.ts

@@ -27,6 +27,9 @@ export interface ActivityPubActor {
     publicKeyPem: string
   }
 
+  // Lemmy attribute for groups
+  postingRestrictedToMods?: boolean
+
   image?: ActivityIconObject | ActivityIconObject[]
   icon?: ActivityIconObject | ActivityIconObject[]
 

server/core/helpers/activity-pub-utils.ts

@@ -192,6 +192,9 @@ const contextStore: { [ id in ContextType ]: (string | { [ id: string ]: string
       '@id': 'pt:support'
     },
 
+    lemmy: 'https://join-lemmy.org/ns#',
+    postingRestrictedToMods: 'lemmy:postingRestrictedToMods',
+
     // TODO: remove in a few versions, introduced in 4.2
     icons: 'as:icon'
   }),

server/core/models/video/video-channel.ts

@@ -825,16 +825,19 @@ export class VideoChannelModel extends SequelizeModel<VideoChannelModel> {
   async toActivityPubObject (this: MChannelAP): Promise<ActivityPubActor> {
     const obj = await this.Actor.toActivityPubObject(this.name)
 
-    return Object.assign(obj, {
+    return {
+      ...obj,
+
       summary: this.description,
       support: this.support,
+      postingRestrictedToMods: true,
       attributedTo: [
         {
           type: 'Person' as 'Person',
           id: this.Account.Actor.url
         }
       ]
-    })
+    }
   }
 
   // Avoid error when running this method on MAccount... | MChannel...