Prevent ActivityPub movedTo recursion (#8092)

Fix #8051

app/services/activitypub/fetch_remote_account_service.rb

@@ -7,14 +7,14 @@ class ActivityPub::FetchRemoteAccountService < BaseService
 
   # Should be called when uri has already been checked for locality
   # Does a WebFinger roundtrip on each call
-  def call(uri, id: true, prefetched_body: nil)
+  def call(uri, id: true, prefetched_body: nil, break_on_redirect: false)
     @json = if prefetched_body.nil?
               fetch_resource(uri, id)
             else
               body_to_json(prefetched_body)
             end
 
-    return unless supported_context? && expected_type?
+    return if !supported_context? || !expected_type? || (break_on_redirect && @json['movedTo'].present?)
 
     @uri      = @json['id']
     @username = @json['preferredUsername']

app/services/activitypub/process_account_service.rb

@@ -175,7 +175,7 @@ class ActivityPub::ProcessAccountService < BaseService
 
   def moved_account
     account   = ActivityPub::TagManager.instance.uri_to_resource(@json['movedTo'], Account)
-    account ||= ActivityPub::FetchRemoteAccountService.new.call(@json['movedTo'], id: true)
+    account ||= ActivityPub::FetchRemoteAccountService.new.call(@json['movedTo'], id: true, break_on_redirect: true)
     account
   end