Function build_intent 

pub fn build_intent(
    prompt: Option<String>,
    model: Option<String>,
    session: Option<String>,
    issue: Option<String>,
    default_session: impl FnOnce() -> String,
) -> Intent

Build (not record) the Intent for a write from its optional parts. The one implementation lex publish, lex ws transform and the HTTP write endpoints share, so an unattributed write looks the same whichever door it came through. default_session is only called when session is None.