[MailSystem] Handle Attachments #105
Description
Handle attachments for both Embeds and Message sending.
- Embeds need to set the image and content
- Messages can just send as content
One concern is, I don't believe there's a reliable way to send images for transcripts, especially if it's done by the staff team (as you can't delete the message that sent the image or else it'll disappear), so #104 won't be able to handle images.