Add support for editing for published statuses (#16697)

* Add support for editing for published statuses

* Fix references to stripped-out code

* Various fixes and improvements

* Further fixes and improvements

* Fix updates being potentially sent to unauthorized recipients

* Various fixes and improvements

* Fix wrong words in test

* Fix notifying accounts that were tagged but were not in the audience

* Fix mistake

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