Start writing real serve tests

src/session_id.rs

@@ -1,3 +1,5 @@
+use std::fmt;
+
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
@@ -13,3 +15,9 @@ impl SessionId {
         SessionId(Uuid::new_v4())
     }
 }
+
+impl fmt::Display for SessionId {
+    fn fmt(&self, writer: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(writer, "{}", self.0)
+    }
+}