Allow customizing form notification emails

Problem

Form submissions currently use Webstudio's default sender details and email template. Site owners cannot set the sender name or sender email address, and they cannot change the content or translate the email they receive.

This makes it hard to match form notifications to a site's brand or use the right language for the team receiving them.

Desired result

Let site owners configure form notification emails, including:

• sender name
• sender email address, subject to email delivery and security rules
• email template and content
• language or translated text

The settings should be clear in the Builder and work for supported form submission setups.

Open questions

• Which sender addresses can be used safely and reliably?
• Do custom domains need to be verified before they can be used as the sender?
• Should the same settings apply to all forms in a project, or can each form have its own settings?
• Which parts of the current email can be customized?

Discussion

https://discord.com/channels/955905230107738152/955905231227609158/1546368437805391943