Store the sent emails

One feature @paulcsmith [mentioned before](https://github.com/luckyframework/breeze/pull/2#issuecomment-784313285) was having a way to view the sent emails. Right now, when you send an email in development, it's thrown in to the log with both the text and html versions which 1. makes the log super messy, and 2. can make it difficult to find links you're supposed to click (e.g. confirm email). Have you seen the [markup](https://github.com/ColorlibHQ/email-templates/blob/master/1/index.html) that goes in to some of these emails? 😬

This feature could live on the same page as the email previews index, and just in a panel below. I seem them looking similar to the queries page, and clicking through just renders that email. This also means that we'd have to create a new model to store the emails, but the benefit would be essentially using it as your own personal mailbox.

Start by reviewing the email previews index and the queries page, which are named as UI references. Define the storage model and dashboard flow for sent emails, then verify that development emails appear below the previews and can be opened to render the email.

Written by the indexing model from the issue text.