We need a better way to test and deploy templates from local dev

There is a prior request to ask for [better testing support for templates]( but it was closed because "we have testing now". I will submit that the testing we have is inadequate for the following reasons: 1. There is no way to trigger Supabase to send the rendered templates (preferably with some place-holder values). * Running through the hoops of your own app UI make it slow to iterate template designs. 2. There is no way to send test messages to *real* email clients. * You need to see how your templates render in the clients your customers will be using (gmail, outlook, apple mail, etc), not just the Inbucket web view of it. * I cannot find any settings to enable using a real SMTP server actually deliver mail. * Trying to configure, for example, gmail to fetch via inbucket's POP server behind a firewall running on a laptop with a dynamic IP address is really a non-starter. Also, there really needs to be a way to use the CLI to [push the temp…