replies to emails that aren't in the database

[azliu0]

Currently, inside of emails.py, we do not handle emails that are replies to emails that aren't in the database (see the TODO in the file).

This case should be handled. I can think of two ways:

1. ignore the previous context from all other emails in the thread, and start a fresh thread with this email only. all generated responses would only have context from this point in the thread
2. take the full body, including all other emails in the thread, and do something with it. this could include only rendering the current email, and using the full body as context, or figuring out a way to render the entire chain (with possibly missing information)

There could be other ways to handle this, but we should probably do something at some point.