Expose the splitter key type

implementation/src/main/java/io/smallrye/mutiny/operators/multi/split/MultiSplitter.java

@@ -51,13 +51,15 @@ public class MultiSplitter<T, K extends Enum<K>> {
     private final Function<T, K> splitter;
     private final ConcurrentHashMap<K, SplitMulti.Split> splits;
     private final int requiredNumberOfSubscribers;
+    private final Class<K> keyType;
 
     public MultiSplitter(Multi<? extends T> upstream, Class<K> keyType, Function<T, K> splitter) {
         this.upstream = nonNull(upstream, "upstream");
         if (!nonNull(keyType, "keyType").isEnum()) {
             // Note: the Java compiler enforces a type check on keyType being some enum, so this branch is only here for added peace of mind
             throw new IllegalArgumentException("The key type must be that of an enumeration");
         }
+        this.keyType = keyType;
         this.splitter = nonNull(splitter, "splitter");
         this.splits = new ConcurrentHashMap<>();
         this.requiredNumberOfSubscribers = keyType.getEnumConstants().length;
@@ -74,6 +76,15 @@ public Multi<T> get(K key) {
         return Infrastructure.onMultiCreation(new SplitMulti(key));
     }
 
+    /**
+     * Get the (enum) key type.
+     *
+     * @return the key type
+     */
+    public Class<K> keyType() {
+        return keyType;
+    }
+
     private enum State {
         INIT,
         AWAITING_SUBSCRIPTION,

implementation/src/test/java/io/smallrye/mutiny/operators/multi/split/MultiSplitterTest.java

@@ -48,6 +48,8 @@ void rejectNegativeDemand() {
     @Test
     void checkBasicBehavior() {
         var splitter = evenOddSplitter();
+        assertThat(splitter.keyType()).isEqualTo(OddEven.class);
+
         var odd = splitter.get(OddEven.ODD)
                 .subscribe().withSubscriber(AssertSubscriber.create());
         var even = splitter.get(OddEven.EVEN)