Reduce usage of LD signatures (#9659)

* Do not LDS-sign Follow, Accept, Reject, Undo, Block

* Do not use LDS for Create activities of private toots

* Minor cleanup

* Ignore unsigned activities instead of misattributing them

* Use status.distributable? instead of querying visibility directly

app/services/activitypub/process_collection_service.rb

@@ -27,7 +27,7 @@ class ActivityPub::ProcessCollectionService < BaseService
   private
 
   def different_actor?
-    @json['actor'].present? && value_or_id(@json['actor']) != @account.uri && @json['signature'].present?
+    @json['actor'].present? && value_or_id(@json['actor']) != @account.uri
   end
 
   def process_items(items)

app/services/after_block_domain_from_account_service.rb

@@ -31,11 +31,11 @@ class AfterBlockDomainFromAccountService < BaseService
 
     return unless follow.account.activitypub?
 
-    json = Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    json = ActiveModelSerializers::SerializableResource.new(
       follow,
       serializer: ActivityPub::RejectFollowSerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(@account))
+    ).to_json
 
     ActivityPub::DeliveryWorker.perform_async(json, @account.id, follow.account.inbox_url)
   end

app/services/authorize_follow_service.rb

@@ -24,11 +24,11 @@ class AuthorizeFollowService < BaseService
   end
 
   def build_json(follow_request)
-    Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    ActiveModelSerializers::SerializableResource.new(
       follow_request,
       serializer: ActivityPub::AcceptFollowSerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(follow_request.target_account))
+    ).to_json
   end
 
   def build_xml(follow_request)

app/services/block_service.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 class BlockService < BaseService
-  include StreamEntryRenderer
-
   def call(account, target_account)
     return if account.id == target_account.id
 
@@ -27,11 +25,11 @@ class BlockService < BaseService
   end
 
   def build_json(block)
-    Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    ActiveModelSerializers::SerializableResource.new(
       block,
       serializer: ActivityPub::BlockSerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(block.account))
+    ).to_json
   end
 
   def build_xml(block)

app/services/follow_service.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 class FollowService < BaseService
-  include StreamEntryRenderer
-
   # Follow a remote user, notify remote user about the follow
   # @param [Account] source_account From which to follow
   # @param [String, Account] uri User URI to follow in the form of username@domain (or account record)
@@ -82,10 +80,10 @@ class FollowService < BaseService
   end
 
   def build_json(follow_request)
-    Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    ActiveModelSerializers::SerializableResource.new(
       follow_request,
       serializer: ActivityPub::FollowSerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(follow_request.account))
+    ).to_json
   end
 end

app/services/process_mentions_service.rb

@@ -60,11 +60,13 @@ class ProcessMentionsService < BaseService
   end
 
   def activitypub_json
-    @activitypub_json ||= Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    return @activitypub_json if defined?(@activitypub_json)
+    payload = ActiveModelSerializers::SerializableResource.new(
       @status,
       serializer: ActivityPub::ActivitySerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(@status.account))
+    ).as_json
+    @activitypub_json = Oj.dump(@status.distributable? ? ActivityPub::LinkedDataSignature.new(payload).sign!(@status.account) : payload)
   end
 
   def resolve_account_service

app/services/reject_follow_service.rb

@@ -19,11 +19,11 @@ class RejectFollowService < BaseService
   end
 
   def build_json(follow_request)
-    Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    ActiveModelSerializers::SerializableResource.new(
       follow_request,
       serializer: ActivityPub::RejectFollowSerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(follow_request.target_account))
+    ).to_json
   end
 
   def build_xml(follow_request)

app/services/unblock_service.rb

@@ -20,11 +20,11 @@ class UnblockService < BaseService
   end
 
   def build_json(unblock)
-    Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    ActiveModelSerializers::SerializableResource.new(
       unblock,
       serializer: ActivityPub::UndoBlockSerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(unblock.account))
+    ).to_json
   end
 
   def build_xml(block)

app/services/unfollow_service.rb

@@ -43,11 +43,11 @@ class UnfollowService < BaseService
   end
 
   def build_json(follow)
-    Oj.dump(ActivityPub::LinkedDataSignature.new(ActiveModelSerializers::SerializableResource.new(
+    ActiveModelSerializers::SerializableResource.new(
       follow,
       serializer: ActivityPub::UndoFollowSerializer,
       adapter: ActivityPub::Adapter
-    ).as_json).sign!(follow.account))
+    ).to_json
   end
 
   def build_xml(follow)