Project 2022-12-055, task 4: Add compose/reply/send functionality to the e-mail client

[BjarniRunar]

The goal of this task is to flesh out the required back-end API methods and deliver a text-mode tool which is capable of composing new e-mails, adding them to an outbox and then sending them via. SMTP.

Milestone(s):

• Implement "drafts", "outbox" and "sent" (local or remote)
• Implement SMTP client functionality
• Implement e-mail address search API
• Add compose, reply and forward views to the Urwid application
• Implement "crypto policy recommendation" API (stretch goal)
• Implement OpenPGP encryption and signatures (stretch goal)
• Document how to use relevant moggie APIs from the CLI or as a web API