Campaigns ride out an email outage, and safer API keys

A round of work that keeps Solstral steady when something around it goes wrong.

• Campaigns wait out an outage. If the email service is briefly unreachable, the people a campaign was sending to are shown as waiting and are sent automatically when it is back, instead of being marked as failed.
• API keys. Each key now shows who made it, and when that person is removed or deactivated the keys they made stop working, like the keys that act as them already did.
• Formula fields stop at 32,767 characters of text, the same limit as a spreadsheet cell.
• Flows. A Format data step's regular expression now runs in time that can't run away, whatever the pattern; back-references and look-arounds aren't supported, and the builder says so as you type.
• Booking pages on a workspace whose sending hasn't been reviewed yet count their emails to bookers toward the daily allowance, and use the standard wording until the review.