feat: complete session preferences and PAM fixture gates

crates/latchd-core/src/session.rs

@@ -26,10 +26,12 @@ use crate::{
     error::{Error, ResultExt, io_error},
 };
 use rand::RngCore;
+use serde::{Deserialize, Serialize};
 use signal_hook::{consts::SIGUSR1, flag};
 
 /// A session family supported by latchd.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
 pub enum SessionKind {
     /// A login shell on the current virtual terminal.
     Tty,