Add MachineDomainKeys for shared machine domain extraction.

Centralizes domain key normalization from config class names so Standard* machines map to ORDER/DOCUMENT/USER consistently.

Co-authored-by: Cursor <cursoragent@cursor.com>

state_machine_exporter/src/main/java/click/kamil/springstatemachineexporter/analysis/enricher/MachineDomainKeys.java

@@ -0,0 +1,41 @@
+package click.kamil.springstatemachineexporter.analysis.enricher;
+
+import java.util.List;
+import java.util.Locale;
+
+/**
+ * Extracts normalized domain keys from state machine configuration class names
+ * (e.g. {@code StandardOrderStateMachineConfiguration} → {@code ORDER}).
+ */
+public final class MachineDomainKeys {
+
+    private MachineDomainKeys() {
+    }
+
+    public static String extractMachineDomainKey(String machineName) {
+        String simple = machineName.substring(machineName.lastIndexOf('.') + 1);
+        String upper = simple.toUpperCase(Locale.ROOT);
+        for (String marker : List.of("STATEMACHINECONFIGURATION", "STATEMACHINE", "CONFIGURATION", "CONFIG")) {
+            int idx = upper.indexOf(marker);
+            if (idx > 0) {
+                return normalizeDomainKey(upper.substring(0, idx));
+            }
+        }
+        int stateIdx = upper.indexOf("STATE");
+        if (stateIdx > 0) {
+            return normalizeDomainKey(upper.substring(0, stateIdx));
+        }
+        return normalizeDomainKey(upper);
+    }
+
+    private static String normalizeDomainKey(String domain) {
+        if (domain == null || domain.isEmpty()) {
+            return domain;
+        }
+        String upper = domain.toUpperCase(Locale.ROOT);
+        if (upper.startsWith("STANDARD") && upper.length() > "STANDARD".length()) {
+            return upper.substring("STANDARD".length());
+        }
+        return upper;
+    }
+}