satisfy input_iterator and indirectly_readable

Author: soheilshahrouz

libs/libvtrutil/src/vtr_strong_id_range.h

@@ -46,9 +46,9 @@ class StrongIdIterator {
     using difference_type = ssize_t;
 
     ///@brief Dereference operator (*)
-    StrongId& operator*() {
+    StrongId operator*() const {
         VTR_ASSERT_SAFE(bool(id_));
-        return this->id_;
+        return id_;
     }
 
     ///@brief += operator
@@ -75,6 +75,14 @@ class StrongIdIterator {
         return *this;
     }
 
+    ///@brief Post-increment operator
+    StrongIdIterator operator++(int) {
+        VTR_ASSERT_SAFE(bool(id_));
+        StrongIdIterator temp = *this;  // Create a copy of the current object
+        ++(*this);                      // Use the pre-increment operator to increment
+        return temp;                    // Return the copy
+    }
+
     ///@brief Decremment operator
     StrongIdIterator& operator--() {
         VTR_ASSERT_SAFE(bool(id_));