feat: add Interval record to represent start and end points with overlap functionality

src/main/java/de/th_luebeck/ws25/Interval.java

@@ -0,0 +1,18 @@
+package de.th_luebeck.ws25;
+
+public record Interval(int start, int end) {
+
+    public int length() {
+        return end - start + 1;
+    }
+
+    public boolean overlaps(Interval other) {
+        return this.start <= other.end && other.start <= this.end;
+    }
+
+    public int overlapSize(Interval other) {
+        int a = Math.max(this.start, other.start);
+        int b = Math.min(this.end, other.end);
+        return Math.max(0, b - a + 1);
+    }
+}