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

Conflicts:
- `app/lib/activitypub/activity/create.rb`:
  Upstream refactored how `Create` activities are handled and how values are
  extracted from `Create`d objects. This conflicted with how glitch-soc
  supported the `directMessage` flag to explicitly distinguish between
  limited and direct messages.
  Ported glitch-soc's changes to latest upstream changes.
- `app/services/fan_out_on_write_service.rb`:
  Upstream largely refactored that file and changed some of the logic.
  This conflicted with glitch-soc's handling of the direct timeline and
  the options to allow replies and boosts in public feeds.
  Ported those glitch-soc changes on top of latest upstream changes.
- `app/services/process_mentions_service.rb`:
  Upstream refactored to move mention-related ActivityPub deliveries to
  `ActivityPub::DeliveryWorker`, while glitch-soc contained an extra check
  to not send local-only toots to remote mentioned users.
  Took upstream's version, as the check is not needed anymore, since it is
  performed at the `ActivityPub::DeliveryWorker` call site already.
- `app/workers/feed_insert_worker.rb`:
  Upstream added support for `update` toot events, while glitch-soc had
  support for an extra timeline support, `direct`.
  Ported upstream changes and extended them to the `direct` timeline.

Additional changes:
- `app/lib/activitypub/parser/status_parser.rb`:
  Added code to handle the `directMessage` flag and take it into account
  to compute visibility.
- `app/lib/feed_manager.rb`:
  Extended upstream's support of `update` toot events to glitch-soc's
  `direct` timeline.

db/migrate/20210904215403_add_edited_at_to_statuses.rb

@@ -0,0 +1,5 @@
+class AddEditedAtToStatuses < ActiveRecord::Migration[6.1]
+  def change
+    add_column :statuses, :edited_at, :datetime
+  end
+end

db/migrate/20210908220918_create_status_edits.rb

@@ -0,0 +1,13 @@
+class CreateStatusEdits < ActiveRecord::Migration[6.1]
+  def change
+    create_table :status_edits do |t|
+      t.belongs_to :status, null: false, foreign_key: { on_delete: :cascade }
+      t.belongs_to :account, null: true, foreign_key: { on_delete: :nullify }
+      t.text :text, null: false, default: ''
+      t.text :spoiler_text, null: false, default: ''
+      t.boolean :media_attachments_changed, null: false, default: false
+
+      t.timestamps
+    end
+  end
+end