Add method to move message into different mailbox

[geerlingguy]

One of the main missing features I just noticed is the ability to move messages into different boxes. Right now, you can read and delete messages, but you can't move them into another box (for archival, sorting, etc.).

This will hopefully be pretty simple.

[geerlingguy]

This should be working (with the patch I just committed above), but the IMAP server I'm using seems to not be happy with the code (I keep getting the error Notice: Unknown: COPY [TRYCREATE] destination mailbox does not exist (errflg=2) in main() (line of ).).

Hopefully someone else can test this elsewhere and make sure it's working correctly.

[github-actions[bot]]

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[github-actions[bot]]

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