Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- `app/services/remove_status_service.rb`:
  Conflict caused by us having a distinc Direct timeline.
  Ported upstream changes.
- `app/javascript/mastodon/features/compose/components/compose_form.js`:
  Conflict between glitch-soc's variable character limit and upstream
  refactoring that part of the code.
  Ported upstream changes.

app/lib/status_reach_finder.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+class StatusReachFinder
+  def initialize(status)
+    @status = status
+  end
+
+  def inboxes
+    Account.where(id: reached_account_ids).inboxes
+  end
+
+  private
+
+  def reached_account_ids
+    [
+      replied_to_account_id,
+      reblog_of_account_id,
+      mentioned_account_ids,
+      reblogs_account_ids,
+      favourites_account_ids,
+      replies_account_ids,
+    ].tap do |arr|
+      arr.flatten!
+      arr.compact!
+      arr.uniq!
+    end
+  end
+
+  def replied_to_account_id
+    @status.in_reply_to_account_id
+  end
+
+  def reblog_of_account_id
+    @status.reblog.account_id if @status.reblog?
+  end
+
+  def mentioned_account_ids
+    @status.mentions.pluck(:account_id)
+  end
+
+  def reblogs_account_ids
+    @status.reblogs.pluck(:account_id)
+  end
+
+  def favourites_account_ids
+    @status.favourites.pluck(:account_id)
+  end
+
+  def replies_account_ids
+    @status.replies.pluck(:account_id)
+  end
+end