Prior to this commit, the composer was based on a map[string]string.
While this approach was very versatile, it lead to a constant encoding / decoding
of addresses and other headers.
This commit switches to a different model, where the composer is based on a header.
Commands which want to interact with it can simply set some defaults they would
like to have. Users can overwrite them however they like.
In order to get access to the functions generating / getting the msgid go-message
was upgraded.
This piggybacks on the existing IMAP support, and uses the same
configuration format (my local testing example has the IMAP and SMTP
lines almost copy-pasted from one another).
It's a little clumsy in that a new token is negotiated for every
`Send()` command, but it's a start...
The following functionalities are added to configure aerc ui styles.
- Read stylesets from file with very basic fnmatch wildcard matching
- Add default styleset
- Support different stylesets as part of UiConfig allowing contextual
styles.
- Move widgets/ui elements to use the stylesets.
- Add configuration manual for the styleset
- Add maildir flags to complement a messages imap flags
- Set the "seen" flag on sent messages when using the maildir backend
- Cleanup AppendMessage interface to use models.Flag for both IMAP and
maildir
