[FIX] calendar: templates with right lang

Before this commit, the standard mail templates for calendar
did not have a language

After this commit, we set it to the the partner's language

OPW 1946686

closes odoo/odoo#32717

Signed-off-by: Lucas Perais (lpe) <lpe@odoo.com>

addons/calendar/data/mail_data.xml

@@ -8,6 +8,7 @@
             <field name="email_from">${object.event_id.user_id.email or ''}</field>
             <field name="email_to" >${('' if object.partner_id and object.partner_id.email and object.partner_id.email==object.email else object.email|safe)}</field>
             <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and object.partner_id.id or False }</field>
+            <field name="lang">${object.partner_id.lang}</field>
             <field name="body_html" type="html">
 <div>
     % set colors = {'needsAction': 'grey', 'accepted': 'green', 'tentative': '#FFFF00',  'declined': 'red'}
@@ -91,6 +92,7 @@
             <field name="email_from">${object.event_id.user_id.email or ''}</field>
             <field name="email_to" >${('' if object.partner_id and object.partner_id.email and object.partner_id.email==object.email else object.email|safe)}</field>
             <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and object.partner_id.id or False }</field>
+            <field name="lang">${object.partner_id.lang}</field>
             <field name="body_html" type="html">
 <div>
     % set colors = {'needsAction': 'grey', 'accepted': 'green', 'tentative': '#FFFF00',  'declined': 'red'}
@@ -174,6 +176,7 @@
             <field name="email_from">${object.event_id.user_id.email or ''}</field>
             <field name="email_to" >${('' if object.partner_id and object.partner_id.email and object.partner_id.email==object.email else object.email|safe)}</field>
             <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and object.partner_id.id or False }</field>
+            <field name="lang">${object.partner_id.lang}</field>
             <field name="body_html" type="html">
 <div>
     % set colors = {'needsAction': 'grey', 'accepted': 'green', 'tentative': '#FFFF00',  'declined': 'red'}