Account deletion (#3728)

* Add form for account deletion

* If avatar or header are gone from source, remove them

* Add option to have SuspendAccountService remove user record, add tests

* Exclude suspended accounts from search

app/models/form/delete_confirmation.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class Form::DeleteConfirmation
+  include ActiveModel::Model
+
+  attr_accessor :password
+end