Set secrete_key to fix cookie persistence

.env.example

@@ -1,3 +1,5 @@
 CLIENT_ID=
 CLIENT_SECRET=
-DOMAIN=https://tegakituesday.com/
+DOMAIN=https://tegakituesday.com/
+# head -c64 /dev/urandom | base64
+SECRET=

src/main.rs

@@ -309,8 +309,10 @@ impl User {
 
 #[launch]
 fn rocket() -> _ {
-    let config = rocket::Config::figment().merge(("port", 1313));
     dotenv::dotenv().expect("Failed to load .env file");
+    let config = rocket::Config::figment()
+        .merge(("port", 1313))
+        .merge(("secret_key", env::var("SECRET").expect("Must have SECRET defined in .env for private cookie persistence")));
     rocket::custom(config)
         .mount(
             "/",