We add method getMountainPosition who was in FirefighterBoard in order to respect SOLID principe

src/main/java/model/Mountain.java

@@ -3,7 +3,9 @@ package model;
 import util.Position;
 
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 public class Mountain {
     private final Position position;
@@ -15,4 +17,10 @@ public class Mountain {
         return position;
     }
 
+    public static Set<Position> getMountainPositions(List<Mountain> mountains) {
+        return mountains.stream()
+                .map(Mountain::getPosition)
+                .collect(Collectors.toSet());
+    }
+
 }