Currently an error is generated when the user tries to save an
appointment as follows:
- Install the appointment_google_calendar module without demo data
- Create a new appointment as below:
      - Remove Organizer (user_id)
      - Set the Google Meet link inside VideocallURL, e.g., https://meet.google.com/aaa-aaa-aaa
- An error occurs in the log and a message is shown to the user when save the record
- Also, an error occurs when trying to preview `Appointment: Attendee Invitation`
  after creating appointment as follows:
      - Set the Google Meet link inside Videocall URL > save
      - Remove Organizer (user_id)

Error: 
```
test odoo.addons.mail.models.mail_render_mixin: Failed to render QWeb template for Mail Template: 'Appointment: Appointment Booked' (ID: 12) - Context language:en_US
Target Model: calendar.event
Error: Error while render the template
ValueError: Expected singleton: res.users()
```


This is because the method `is_google_calendar_synced` expected a single
record, but since we removed `user_id` from the event (appointment),
it will generate a singleton error.

This commit will fix the above issue by not calling `is_google_calendar_synced`
when the event does not have `user_id`.

sentry-7393595716

When sending an invoice by email template, dynamic report attachments do not use their configured Printed Report Name. Instead, they fall back to a default naming pattern (e.g. report name + invoice number).

This is due to a difference in flow: sales use the standard mail.compose.message wizard, which correctly applies each report’s print_report_name, while invoices use the dedicated account.move.send flow. In this flow, dynamic report filenames are not computed from the report itself.

To fix this, the send flow is updated so _get_placeholder_mail_template_dynamic_attachments_data computes the filename from each dynamic report. When a print_report_name is defined, it is used. Otherwise, the previous fallback behavior is preserved.

The fix will ensure extra dynamic reports follow their configured printed name.

Steps to reproduce:
1. Go to Settings > Technical > Reporting > Reports and duplicate the standard Invoice report.
2. In the duplicated report, set a custom value in Printed Report Name (e.g. 'CUSTOM_NAME_TEST').
3. Go to Settings > Technical > Email > Templates and open “Invoice: Sending”.
4. Add the duplicated report under Dynamic Reports.
5. Create a customer invoice and confirm it.
3. Click Send (or Send & Print) to open the email preview.

Related Ticket:
opw-6058716