[IMP] mail: reduce message_post query count and clean code

Purpose of this commit is to improve performance of post and notify through
various code improvements.

Containing
  * making of _notify_customize_recipients a mail.thread method;
  * _message_auto_subscribe_followers optimized;
  * renaming and optimisation of _notify_partners;
  * message_post_attachements optization;
  * remove unused mail_post_autofollow_partner_ids context key;
  * minimize message create queries;
  * only check record related access right for thread messages not in pending
    moderation;
  * get attachements from values instead of db;
  * storing lang in ctx from the beginning;
  * don't track on write on attachments;

Related to task 1943901
Linked to PR #32404

odoo/addons/base/models/ir_attachment.py

@@ -11,7 +11,7 @@ from collections import defaultdict
 import uuid
 
 from odoo import api, fields, models, tools, SUPERUSER_ID, _
-from odoo.exceptions import AccessError, ValidationError
+from odoo.exceptions import AccessError, ValidationError, MissingError
 from odoo.tools import config, human_size, ustr, html_escape
 from odoo.tools.mimetypes import guess_mimetype
 
@@ -313,6 +313,8 @@ class IrAttachment(models.Model):
     def _check_serving_attachments(self):
         # restrict writing on attachments that could be served by the
         # ir.http's dispatch exception handling
+        # XDO note: this should be done in check(write), constraints for access rights?
+        # XDO note: if read on sudo, read twice, one for constraints, one for _inverse_datas as user
         if self.env.user._is_admin():
             return
         if self.type == 'binary' and self.url:
@@ -326,13 +328,15 @@ class IrAttachment(models.Model):
         In the 'document' module, it is overriden to relax this hard rule, since
         more complex ones apply there.
         """
+        if self.env.user._is_superuser():
+            return True
         # collect the records to check (by model)
         model_ids = defaultdict(set)            # {model_name: set(ids)}
         require_employee = False
         if self:
             self._cr.execute('SELECT res_model, res_id, create_uid, public, res_field FROM ir_attachment WHERE id IN %s', [tuple(self.ids)])
             for res_model, res_id, create_uid, public, res_field in self._cr.fetchall():
-                if self.env.user.id != SUPERUSER_ID and not self.env.user._is_system() and res_field:
+                if not self.env.user._is_system() and res_field:
                     raise AccessError(_("Sorry, you are not allowed to access this document."))
                 if public and mode == 'read':
                     continue
@@ -488,12 +492,20 @@ class IrAttachment(models.Model):
 
     @api.model_create_multi
     def create(self, vals_list):
+        record_tuple_set = set()
         for values in vals_list:
             # remove computed field depending of datas
             for field in ('file_size', 'checksum'):
                 values.pop(field, False)
             values = self._check_contents(values)
-            self.browse().check('write', values=values)
+            # 'check()' only uses res_model and res_id from values, and make an exists.
+            # We can group the values by model, res_id to make only one query when 
+            # creating multiple attachments on a single record.
+            record_tuple = (values.get('res_model'), values.get('res_id'))
+            record_tuple_set.add(record_tuple)
+        for record_tuple in record_tuple_set:
+            (res_model, res_id) = record_tuple
+            self.check('write', values={'res_model':res_model, 'res_id':res_id})
         return super(IrAttachment, self).create(vals_list)
 
     @api.multi
@@ -504,10 +516,13 @@ class IrAttachment(models.Model):
     def generate_access_token(self):
         if self.access_token:
             return self.access_token
-        access_token = str(uuid.uuid4())
+        access_token = self._generate_access_token()
         self.write({'access_token': access_token})
         return access_token
 
+    def _generate_access_token(self):
+        return str(uuid.uuid4())
+
     @api.model
     def action_get(self):
         return self.env['ir.actions.act_window'].for_xml_id('base', 'action_attachment')