0.16 adds a notmuch insert command which we can use to insert a sent message into the maildir. Should we use it? It could be used if no sent-box setting is present and the version check detects 0.16 or higher.
But the question is if we should insert it with the tag:sent or not. I use afew from a hook to tag sent messages. I will have to test if hooks are run on insert or if notmuch-web should add some config setting to determine what tags to set on sent messages.