Merge branch 'stable-4.3' into glitch-soc/backports-4.3

Conflicts:
- `app/helpers/application_helper.rb`:
  Upstream added a helper where glitch-soc had its own, not really
  a conflict.
  Added upstream's helper.

app/lib/activitypub/activity/create.rb

@@ -42,6 +42,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
   def process_status
     @tags                 = []
     @mentions             = []
+    @unresolved_mentions  = []
     @silenced_account_ids = []
     @params               = {}
 
@@ -55,6 +56,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
     end
 
     resolve_thread(@status)
+    resolve_unresolved_mentions(@status)
     fetch_replies(@status)
     distribute
     forward_for_reply
@@ -197,6 +199,8 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
     return if account.nil?
 
     @mentions << Mention.new(account: account, silent: false)
+  rescue Mastodon::UnexpectedResponseError, HTTP::TimeoutError, HTTP::ConnectionError, OpenSSL::SSL::SSLError
+    @unresolved_mentions << tag['href']
   end
 
   def process_emoji(tag)
@@ -301,6 +305,12 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
     ThreadResolveWorker.perform_async(status.id, in_reply_to_uri, { 'request_id' => @options[:request_id] })
   end
 
+  def resolve_unresolved_mentions(status)
+    @unresolved_mentions.uniq.each do |uri|
+      MentionResolveWorker.perform_in(rand(30...600).seconds, status.id, uri, { 'request_id' => @options[:request_id] })
+    end
+  end
+
   def fetch_replies(status)
     collection = @object['replies']
     return if collection.blank?