fix: normalize MITC4 reference identities

tests/reference/mitc4_reference_comparison.cpp

@@ -120,13 +120,25 @@ double parseFiniteDouble(const std::string& field) {
     return value;
 }
 
+std::string uppercaseAscii(std::string value) {
+    std::transform(
+        value.begin(), value.end(), value.begin(), [](const char character) {
+            return character >= 'a' && character <= 'z'
+                       ? static_cast<char>(character - 'a' + 'A')
+                       : character;
+        });
+    return value;
+}
+
 struct IdentityKey {
     std::string instanceName;
     std::int64_t sourceNodeLabel;
 
-    bool operator<(const IdentityKey& other) const noexcept {
-        if (instanceName != other.instanceName) {
-            return instanceName < other.instanceName;
+    bool operator<(const IdentityKey& other) const {
+        const std::string normalizedInstance = uppercaseAscii(instanceName);
+        const std::string normalizedOther = uppercaseAscii(other.instanceName);
+        if (normalizedInstance != normalizedOther) {
+            return normalizedInstance < normalizedOther;
         }
         return sourceNodeLabel < other.sourceNodeLabel;
     }