Removed the teaser fields from emails

We've removed the following fields from the Email object:

• should_send_teaser
• custom_teaser

This is a completely breaking change with no backwards compatibility or API version. If you're relying on these fields to be present (or are writing to these fields), then:

• You should migrate to using the Email.body field and setting the paywall therein.
• You should email us, because our analysis showed us that nobody was setting these fields programmatically!

You can read more about the decision in the changelog entry for 2025-02-06.