Add first day of the week feature to user settings and calendar functionality

backend/src/data/model.rs

@@ -8,6 +8,10 @@ pub struct User {
     pub name: String,
     pub email: String,
     pub default_servings: u32,
+
+    #[sqlx(try_from = "u8")]
+    pub first_day_of_the_week: Weekday,
+
     pub lang: String,
     pub is_admin: bool,
 }