use Sqlite FTS5 for search, assume correct language codes

app/models/supported_language.rb

@@ -7,4 +7,10 @@ class SupportedLanguage < ApplicationRecord
   validates :code, presence: true, uniqueness: true
   validates :name, presence: true
   validates :native_name, presence: true
+
+  def self.valid_codes
+    Rails.cache.fetch("supported_languages_codes", expires_in: 1.hour) do
+      pluck(:code).map(&:to_s)
+    end
+  end
 end