Filter incoming Announce activities by relation to local activity (#10041)

* Filter incoming Announce activities by relation to local activity

Reject if announcer is not followed by local accounts, and is not
from an enabled relay, and the object is not a local status

Follow-up to #10005

* Fix tests

app/lib/activitypub/activity.rb

@@ -138,11 +138,13 @@ class ActivityPub::Activity
   def status_from_object
     # If the status is already known, return it
     status = status_from_uri(object_uri)
+
     return status unless status.nil?
 
     # If the boosted toot is embedded and it is a self-boost, handle it like a Create
     unless unsupported_object_type?
       actor_id = value_or_id(first_of_value(@object['attributedTo'])) || @account.uri
+
       if actor_id == @account.uri
         return ActivityPub::Activity.factory({ 'type' => 'Create', 'actor' => actor_id, 'object' => @object }, @account).perform
       end
@@ -166,4 +168,16 @@ class ActivityPub::Activity
   ensure
     redis.del(key)
   end
+
+  def fetch?
+    !@options[:delivery]
+  end
+
+  def followed_by_local_accounts?
+    @account.passive_relationships.exists?
+  end
+
+  def requested_through_relay?
+    @options[:relayed_through_account] && Relay.find_by(inbox_url: @options[:relayed_through_account].inbox_url)&.enabled?
+  end
 end