Automatically fall back to email when channel messaging is unavailable

As booking channels increasingly restrict access to guests' email addresses, and guests are becoming more reluctant to share personal information, I find myself relying more and more on channel messaging.

However, channel messaging is not available for direct bookings.

Currently, sending critical messages to guests requires maintaining two separate triggers and two sets of templates: one for channel messages and another for emails, using the condition "Email Address on File is > Has Real Email Address" to determine which one to use.

Feature request:

Automatically use email as the delivery method when no booking channel is connected. Either "always", or with a tick box "Use email fallback when no channel connected".

This would allow us to maintain a single set of triggers and templates, significantly simplifying configuration and ongoing maintenance while ensuring that guests still receive important messages regardless of their booking source.