Revert "[FIX] mail: onchange_template_id"

This reverts commit dc02f773ce.

This commit caused a side-effect that is worse than the issue
it tried to fix, which was purely cosmetic.
Now in mass-mail mode the template is only rendered once
and all recipients receive the same PDF, which completely
defeats the goal of a dynamic report. We have static
attachments for that.

Original fix related to opw-657152
Reverts PR #10568

addons/mail/models/mail_template.py

@@ -493,7 +493,7 @@ class MailTemplate(models.Model):
                 )
 
             # Add report in attachments: generate once for all template_res_ids
-            if template.report_template and not 'report_template_in_attachment' in self.env.context:
+            if template.report_template:
                 for res_id in template_res_ids:
                     attachments = []
                     report_name = self.render_template(template.report_name, template.model, res_id)

addons/mail/wizard/mail_compose_message.py

@@ -187,7 +187,7 @@ class MailComposer(models.TransientModel):
     @api.multi
     def send_mail_action(self):
         # TDE/ ???
-        return self.with_context(report_template_in_attachment=True).send_mail()
+        return self.send_mail()
 
     @api.multi
     def send_mail(self, auto_commit=False):
@@ -346,20 +346,6 @@ class MailComposer(models.TransientModel):
             if template.user_signature and 'body_html' in values:
                 signature = self.env.user.signature
                 values['body_html'] = tools.append_content_to_html(values['body_html'], signature, plaintext=False)
-            if template.report_template:
-                attachment = self.env['ir.attachment']
-                attach = self.generate_attachment_from_report(template_id, res_id)
-                for attach_fname, attach_datas in attach[res_id].pop('attachments', []):
-                    data_attach = {
-                        'name': attach_fname,
-                        'datas': attach_datas,
-                        'datas_fname': attach_fname,
-                        'res_model': 'mail.compose.message',
-                        'res_id': 0,
-                        'type': 'binary',
-                    }
-                values.setdefault('attachment_ids', list()).append(attachment.create(data_attach).id)
-
         elif template_id:
             values = self.generate_email_for_composer(template_id, [res_id])[res_id]
             # transform attachments into attachment_ids; not attached to the document because this will
@@ -390,13 +376,6 @@ class MailComposer(models.TransientModel):
 
         return {'value': values}
 
-    @api.multi
-    def generate_attachment_from_report(self, template_id, res_id):
-        fields = ['attachment_ids']
-        result = self.env['mail.template'].with_context(tpl_partners_only=True).browse(template_id).generate_email([res_id], fields=fields)
-        return result
-
-
     @api.multi
     def save_as_template(self):
         """ hit save as template button: current form value will be a new