fix(ticketing): render email templates without a permission check (backport #369)

[harshtandiya]

What changed

Manual backport of #369 to main — the bot's cherry-pick failed on two import
blocks. main predates Buzz Team Settings, so event_ticket.py there has no
get_event_team_settings import (it falls back to the Buzz Settings single
instead of the team default), and the test module has no set_team_settings
import either. Both hunks resolved by keeping main's imports and adding only
render_email_template. The fix itself applied clean to all three call sites.

One deliberate deviation from #369: TestRenderEmailTemplate used
create_user from test_buzz_team, which does not exist on main (no Buzz
Team doctype), so the Website User is created inline instead.

Original: ticket, booking-confirmation and sponsor pitch-deck emails rendered
their Email Template through frappe's whitelisted get_email_template(), which
reads the template as the session user. Read access is Desk User /
System Manager only, so every attendee-facing send raised PermissionError —
swallowed by on_submit, leaving a confirmed booking and no email.

Demo

No UI change. skip-demo.

Testing

Not run locally — the bench's app checkout is on develop, and migrating it
down to main would drop doctypes. Ruff clean; leaving the suite to CI.
Covered on develop by event_ticket 12, event_booking 40, booking API 33,
sponsorship_enquiry 4.

[greptile-apps]

Greptile Summary

The PR replaces permission-checked Email Template rendering in attendee-facing email paths with a server-side helper so Guest and Website User flows can render configured templates.

• Adds a shared render_email_template utility.
• Uses it for ticket, booking-confirmation, and sponsor pitch-deck emails.
• Adds coverage for Website User and Guest rendering.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete changed-code defects identified.

The new helper preserves the existing formatted-email contract while removing the permission barrier from the three intended guest-facing notification paths, and template selection remains restricted to trusted configuration.

Important Files Changed

Filename	Overview
buzz/utils.py	Adds the shared server-side Email Template rendering helper used by guest-facing notification flows.
buzz/ticketing/doctype/event_ticket/event_ticket.py	Routes configured ticket templates through the new helper while preserving fallback templates and attachment behavior.
buzz/ticketing/doctype/event_booking/event_booking.py	Routes booking-confirmation templates through the new helper without changing recipient, context, or fallback behavior.
buzz/proposals/doctype/sponsorship_enquiry/sponsorship_enquiry.py	Routes sponsor pitch-deck templates through the new helper while preserving event/global precedence and delivery settings.
buzz/ticketing/doctype/event_ticket/test_event_ticket.py	Adds integration coverage proving Website Users and Guest ticket flows can render configured Email Templates.

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