[FIX] sale_coupon: translate email subject and template

Steps:
- Install Sales
- Go to Settings / Translations / Languages
- Install Dutch
- Go to Settings / Users & Companies / Users
- Change demo's language to Dutch
- Go to Sales / Configuration / Settings
- Activate Coupons & Promotions
- Go to Sales / Products / Coupon Programs
- Create a new Coupon Program
- Click Generate Coupon
  - Generation Type: Number of Selected Customers
  - Matching rule: Name contains demo
- Generate
- Go to Settings / Technical / Email / Emails
- Open the email you just sent

Bug:
Parts of the email are not translated

Explanation:
The `lang` field is used to determine the template's language. Coupon
emails where missing one.
Also, the subject of the email wasn't translated.

opw:2467640

closes odoo/odoo#68316

X-original-commit: 6fbca2745a36ade4d8e8bdd2f015fd831b872d67
Signed-off-by: backspac <backspac@users.noreply.github.com>

3 files changed, 11 insertions, 2 deletions

diff --git a/addons/coupon/data/coupon_email_data.xml b/addons/coupon/data/coupon_email_data.xml
index d28e2f80947..71d2f80eb8f 100644
--- a/addons/coupon/data/coupon_email_data.xml
+++ b/addons/coupon/data/coupon_email_data.xml
@@ -7,6 +7,7 @@
          <field name="subject">Your reward coupon from ${object.program_id.company_id.name} </field>
          <field name="email_from">${object.program_id.company_id.email | safe}</field>
          <field name="partner_to">${object.order_id.partner_id.id or object.partner_id.id}</field>
+         <field name="lang">${object.partner_id.lang}</field>
          <field name="body_html" type="html">
 <table border="0" cellpadding="0" cellspacing="0" style="width:100%; margin:0px auto;"><tbody>
     <tr><td valign="top" style="text-align: center; font-size: 14px;">
diff --git a/addons/coupon/i18n/coupon.pot b/addons/coupon/i18n/coupon.pot
index 4eb6d3007a7..05e2694d9fd 100644
--- a/addons/coupon/i18n/coupon.pot
+++ b/addons/coupon/i18n/coupon.pot
@@ -46,6 +46,12 @@ msgid "%s%% discount on total amount"
 msgstr ""
 
 #. module: coupon
+#: code:addons/coupon/wizard/coupon_generate.py:0
+#, python-format
+msgid "%s, a coupon has been generated for you"
+msgstr ""
+
+#. module: coupon
 #: model_terms:ir.ui.view,arch_db:coupon.report_coupon
 msgid "*Valid for following products:"
 msgstr ""
diff --git a/addons/coupon/wizard/coupon_generate.py b/addons/coupon/wizard/coupon_generate.py
index f89ee5558c4..46318b04d38 100644
--- a/addons/coupon/wizard/coupon_generate.py
+++ b/addons/coupon/wizard/coupon_generate.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-from odoo import api, fields, models
+from odoo import _, api, fields, models
 
 import ast
 from odoo.osv import expression
@@ -33,7 +33,9 @@ class CouponGenerate(models.TransientModel):
             for partner in self.env['res.partner'].search(ast.literal_eval(self.partners_domain)):
                 vals.update({'partner_id': partner.id, 'state': 'sent' if partner.email else 'new'})
                 coupon = self.env['coupon.coupon'].create(vals)
-                subject = '%s, a coupon has been generated for you' % (partner.name)
+                context = dict(lang=partner.lang)
+                subject = _('%s, a coupon has been generated for you') % (partner.name)
+                del context
                 template = self.env.ref('coupon.mail_template_sale_coupon', raise_if_not_found=False)
                 if template:
                     email_values = {'email_to': partner.email, 'email_from': self.env.user.email or '', 'subject': subject}