feat(dialogflow): make language_code configurable instead of hardcoded (#13221)

# Pull Request Template

## Description

Please include a summary of the change and issue(s) fixed. Also, mention
relevant motivation, context, and any dependencies that this change
requires.
- Add language_code setting to Dialogflow integration configuration
- Support 'auto' mode to detect language from contact's
additional_attributes
- Fallback to 'en-US' when no language is configured or detected
- Include comprehensive language options (22 languages)
- Add tests for language code configuration scenarios

Fixes #3071

## Type of change

Please delete options that are not relevant.

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality not to work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list any relevant details
for your test configuration.

<img width="815" height="506" alt="Screenshot 2026-01-10 220410"
src="https://github.com/user-attachments/assets/26d2619c-ed42-4c9a-a41d-9fb07ef91a30"
/>


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

lib/integrations/dialogflow/processor_service.rb

@@ -1,6 +1,51 @@
 require 'google/cloud/dialogflow/v2'
 
 class Integrations::Dialogflow::ProcessorService < Integrations::BotProcessorService
+  SUPPORTED_LANGUAGE_CODES = %w[
+    ar
+    en-US
+    en-GB
+    es-ES
+    es-419
+    fr-FR
+    de-DE
+    pt-BR
+    pt-PT
+    it-IT
+    ja-JP
+    ko-KR
+    zh-CN
+    zh-TW
+    hi-IN
+    ru-RU
+    nl-NL
+    pl-PL
+    tr-TR
+    th-TH
+    vi-VN
+    id-ID
+  ].freeze
+  AUTO_LANGUAGE_CODE_MAP = {
+    'ar' => 'ar',
+    'de' => 'de-DE',
+    'en' => 'en-US',
+    'es' => 'es-ES',
+    'fr' => 'fr-FR',
+    'hi' => 'hi-IN',
+    'id' => 'id-ID',
+    'it' => 'it-IT',
+    'ja' => 'ja-JP',
+    'ko' => 'ko-KR',
+    'nl' => 'nl-NL',
+    'pl' => 'pl-PL',
+    'pt' => 'pt-BR',
+    'ru' => 'ru-RU',
+    'th' => 'th-TH',
+    'tr' => 'tr-TR',
+    'vi' => 'vi-VN',
+    'zh' => 'zh-CN'
+  }.freeze
+
   pattr_initialize [:event_name!, :hook!, :event_data!]
 
   private
@@ -84,7 +129,7 @@ class Integrations::Dialogflow::ProcessorService < Integrations::BotProcessorSer
   def detect_intent(session_id, message)
     client = ::Google::Cloud::Dialogflow::V2::Sessions::Client.new
     session = build_session_path(session_id)
-    query_input = { text: { text: message, language_code: 'en-US' } }
+    query_input = { text: { text: message, language_code: dialogflow_language_code } }
     client.detect_intent session: session, query_input: query_input
   end
 
@@ -98,4 +143,30 @@ class Integrations::Dialogflow::ProcessorService < Integrations::BotProcessorSer
       "projects/#{project_id}/locations/#{region}/agent/sessions/#{session_id}"
     end
   end
+
+  def dialogflow_language_code
+    configured_language = hook.settings['language_code'].to_s.strip
+    return 'en-US' if configured_language.blank?
+    return configured_language if configured_language != 'auto'
+
+    normalized_contact_language_code(conversation&.contact&.additional_attributes&.dig('language_code')) || 'en-US'
+  end
+
+  def normalized_contact_language_code(language_code)
+    canonicalized_language_code = canonical_language_code(language_code)
+    return if canonicalized_language_code.blank?
+    return canonicalized_language_code if SUPPORTED_LANGUAGE_CODES.include?(canonicalized_language_code)
+
+    AUTO_LANGUAGE_CODE_MAP[canonicalized_language_code] || AUTO_LANGUAGE_CODE_MAP[canonicalized_language_code.split('-', 2).first]
+  end
+
+  def canonical_language_code(language_code)
+    normalized_language_code = language_code.to_s.tr('_', '-').strip
+    return if normalized_language_code.blank?
+
+    language, region = normalized_language_code.split('-', 2)
+    return language.downcase if region.blank?
+
+    "#{language.downcase}-#{region.upcase}"
+  end
 end