Function fetch_idle

async fn fetch_idle(
    ctx: &Context,
    connection: &mut Imap,
    session: Session,
    folder_meaning: FolderMeaning,
) -> Result<Session>

Implement a single iteration of IMAP loop.

This function performs all IMAP operations on a single folder, selecting it if necessary and handling all the errors. In case of an error, an error is returned and connection is dropped, otherwise connection is returned.