Add user content translations with configurable backends (#19218)

app/lib/translation_service.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class TranslationService
+  class Error < StandardError; end
+  class NotConfiguredError < Error; end
+  class TooManyRequestsError < Error; end
+  class QuotaExceededError < Error; end
+  class UnexpectedResponseError < Error; end
+
+  def self.configured
+    if ENV['DEEPL_API_KEY'].present?
+      TranslationService::DeepL.new(ENV.fetch('DEEPL_PLAN', 'free'), ENV['DEEPL_API_KEY'])
+    elsif ENV['LIBRE_TRANSLATE_ENDPOINT'].present?
+      TranslationService::LibreTranslate.new(ENV['LIBRE_TRANSLATE_ENDPOINT'], ENV['LIBRE_TRANSLATE_API_KEY'])
+    else
+      raise NotConfiguredError
+    end
+  end
+
+  def translate(_text, _source_language, _target_language)
+    raise NotImplementedError
+  end
+end