[FIX] im_livechat: display chatbot in website or user language

Steps to reproduce:

  - Install the module `crm_livechat`
  - Activate another language (e.g. fr_FR)
  - Open a new incognito window and go to the website
  - On website, switch to the activated language
  - Open contact page
  - Open the chatbot

Issue:

  The chatbot is displayed in `en_US`.

Cause:

  The chatbot is displayed in the current user language (not website
  language).
  Public user have by default `en_US` as language.

Solution:

  Retrieve the chatbot with the website activated language if set,
  otherwise, retrieve the chatbot in the user language.
  Fallback on `en_US`.

opw-3284807

closes odoo/odoo#126341

Signed-off-by: Matthieu Stockbauer (tsm) <tsm@odoo.com>

addons/im_livechat/controllers/main.py

@@ -65,6 +65,8 @@ class LivechatController(http.Controller):
         # find the first matching rule for the given country and url
         matching_rule = request.env['im_livechat.channel.rule'].sudo().match_rule(channel_id, url, country_id)
         if matching_rule and (not matching_rule.chatbot_script_id or matching_rule.chatbot_script_id.script_step_ids):
+            frontend_lang = request.httprequest.cookies.get('frontend_lang', request.env.user.lang or 'en_US')
+            matching_rule = matching_rule.with_context(lang=frontend_lang)
             rule = {
                 'action': matching_rule.action,
                 'auto_popup_timer': matching_rule.auto_popup_timer,
@@ -134,7 +136,8 @@ class LivechatController(http.Controller):
 
         chatbot_script = False
         if chatbot_script_id:
-            chatbot_script = request.env['chatbot.script'].sudo().browse(chatbot_script_id)
+            frontend_lang = request.httprequest.cookies.get('frontend_lang', request.env.user.lang or 'en_US')
+            chatbot_script = request.env['chatbot.script'].sudo().with_context(lang=frontend_lang).browse(chatbot_script_id)
 
         return request.env["im_livechat.channel"].with_context(lang=False).sudo().browse(channel_id)._open_livechat_mail_channel(
             anonymous_name,