[REF] mail: improve propagation and setup of render context when post…

…ing messages

PURPOSE

Purpose of this commit is to cleanup flow of values going through message_post
and its sub methods until email generation for notifications.

SPECIFICATIONS

Ensure some values are given directly when creating message linked to post
methods to avoid browsing message when value is not known. Notably make
signature propagation (add_sign) more explicit in message_post and its sub
methods (notify, log, ...).

Prepare future language related improvements by allowing to force company and
lang values for rendering context. Also add ``is_html_empty`` tool method to
use it in notification templates. It will be used notably to check for empty
html blocks, e.g. user signature.

Rename some internal variables to better understand their purpose.

Finally update some outdated and/or badly indented docstrings.

Task-2726501 (Mail: Propagate message values in post methods)

Part-of: #82167

addons/mail/models/mail_template.py

@@ -7,6 +7,7 @@
 
 from odoo import _, api, fields, models, tools, Command
 from odoo.exceptions import UserError
+from odoo.tools import is_html_empty
 
 _logger = logging.getLogger(__name__)
 
@@ -301,10 +302,20 @@ def send_mail(self, res_id, force_send=False, raise_exception=False, email_value
                     model = model.with_context(lang=lang)
 
                 template_ctx = {
+                    # message
                     'message': self.env['mail.message'].sudo().new(dict(body=values['body_html'], record_name=record.display_name)),
+                    'subtype': self.env['mail.message.subtype'].sudo(),
+                    # record
                     'model_description': model.display_name,
-                    'company': 'company_id' in record and record['company_id'] or self.env.company,
                     'record': record,
+                    'record_name': False,
+                    # user / environment
+                    'company': 'company_id' in record and record['company_id'] or self.env.company,
+                    'email_add_signature': False,
+                    'signature': '',
+                    'website_url': '',
+                    # tools
+                    'is_html_empty': is_html_empty,
                 }
                 body = template._render(template_ctx, engine='ir.qweb', minimal_qcontext=True)
                 values['body_html'] = self.env['mail.render.mixin']._replace_local_links(body)