[FIX] base_usability: ir_mail_server avoid breaking Bcc

fix code for smtp_session in inherit of send_email()
Disable module base_mail_sender_bcc that just doesn't work in v16 ; as it's a design problem, I don't plan to fix it.

base_mail_sender_bcc/__manifest__.py

@@ -17,5 +17,8 @@ With this module, when Odoo sends an outgoing email, it adds the sender as Bcc (
     'author': 'Akretion',
     'website': 'https://github.com/akretion/odoo-usability',
     'depends': ['base'],
-    'installable': True,
+    # I set it to False, because this module doesn't work because of send_validated_to in context
+    # cf method _prepare_email_message()
+    # We should now use the module mail_composer_cc_bcc from OCA/social (moved to OCA/mail)
+    'installable': False,
 }

base_usability_akretion/models/ir_mail_server.py

@@ -18,21 +18,24 @@ class IrMailServer(models.Model):
             smtp_ssl_certificate=None, smtp_ssl_private_key=None,
             smtp_debug=False, smtp_session=None):
         # Start copy from native method
-        smtp = smtp_session
-        if not smtp:
-            smtp = self.connect(
+        if not smtp_session:
+            smtp_session = self.connect(
                 smtp_server, smtp_port, smtp_user, smtp_password, smtp_encryption,
-                smtp_from=message['From'], ssl_certificate=smtp_ssl_certificate, ssl_private_key=smtp_ssl_private_key,
-                smtp_debug=smtp_debug, mail_server_id=mail_server_id,)
-
+                smtp_from=message['From'], ssl_certificate=smtp_ssl_certificate,
+                ssl_private_key=smtp_ssl_private_key,
+                smtp_debug=smtp_debug, mail_server_id=mail_server_id)
+        # _prepare_email_message() will remove the Bcc field in message
+        # that's why we need to save it and re-inject it in message
+        email_bcc = message['Bcc']
         smtp_from, smtp_to_list, message = self._prepare_email_message(
-            message, smtp)
+            message, smtp_session)
+        message['Bcc'] = email_bcc
         # End copy from native method
         logger.info(
             "Sending email from '%s' to '%s' Cc '%s' Bcc '%s' "
-            "with subject '%s'",
+            "with subject '%s'. smtp_to_list=%s",
             smtp_from, message.get('To'), message.get('Cc'),
-            message.get('Bcc'), message.get('Subject'))
+            message.get('Bcc'), message.get('Subject'), smtp_to_list)
         return super().send_email(
             message, mail_server_id=mail_server_id,
             smtp_server=smtp_server, smtp_port=smtp_port,