Move valid_residents to the scheduler impl and simplify it

src-tauri/src/slot.rs

@@ -77,6 +77,18 @@ impl Slot {
         self.day.greater_than(&Day(limit))
     }
 
+    pub fn other_position(&self) -> Self {
+        let other_pos = match self.position {
+            ShiftPosition::First => ShiftPosition::Second,
+            ShiftPosition::Second => ShiftPosition::First,
+        };
+
+        Self {
+            day: self.day,
+            position: other_pos,
+        }
+    }
+
     pub fn default() -> Self {
         Self {
             day: Day(1),