Adds some validation to new user registration.

backend/App.toml.example

@@ -0,0 +1,8 @@
+#Copy this file over to Rocket.toml after changing all relevant values.
+
+[default]
+jwt_secret = "some really good secret"
+
+[global.databases]
+gamenight_database = { url = "gamenight.sqlite" }
+