Add: #87 フォロワーのみに購読を許可する設定 (#239)

* Wip: マイグレーション、設定など一式

* Fix test

* Fix test

* Fix: マスター用の設定を他サーバーに送信しないよう修正

* DTL、外部サーバーの情報受け入れのテストを追加

* スペルミスを修正

* Web画面に設定項目追加

* 既存の`master_settings`を上書きしないよう修正

app/services/activitypub/process_account_service.rb

@@ -83,7 +83,6 @@ class ActivityPub::ProcessAccountService < BaseService
     @account.suspension_origin = :local if auto_suspend?
     @account.silenced_at       = domain_block.created_at if auto_silence?
     @account.searchability     = :direct   # not null
-    @account.dissubscribable   = false     # not null
 
     set_immediate_protocol_attributes!
 
@@ -125,8 +124,8 @@ class ActivityPub::ProcessAccountService < BaseService
     @account.discoverable            = @json['discoverable'] || false
     @account.indexable               = @json['indexable'] || false
     @account.searchability           = searchability_from_audience
-    @account.dissubscribable         = !subscribable(@account.note)
     @account.settings                = other_settings
+    @account.master_settings         = (@account.master_settings || {}).merge(master_settings(@account.note))
     @account.memorial                = @json['memorial'] || false
   end
 
@@ -320,14 +319,24 @@ class ActivityPub::ProcessAccountService < BaseService
     @subscribable_by = as_array(@json['subscribableBy']).map { |x| value_or_id(x) }
   end
 
-  def subscribable(note)
+  def subscription_policy(note)
     if subscribable_by.nil?
-      note.exclude?('[subscribable:no]')
+      note.include?('[subscribable:no]') ? :block : :allow
+    elsif subscribable_by.any? { |uri| ActivityPub::TagManager.instance.public_collection?(uri) }
+      :allow
+    elsif subscribable_by.include?(@account.followers_url)
+      :followers_only
     else
-      subscribable_by.any? { |uri| ActivityPub::TagManager.instance.public_collection?(uri) }
+      :block
     end
   end
 
+  def master_settings(note)
+    {
+      'subscription_policy' => subscription_policy(note),
+    }
+  end
+
   def other_settings
     return {} unless @json['otherSetting'].is_a?(Array)