Fixed Java issue in Subscription DSL

changelog.md

@@ -1,3 +1,13 @@
+### Next version
+* Fixed issue in [Subscription DSL](https://occurrent.org/documentation#subscription-dsl) when using "subscribe" functions with a single event type different from the "base event type", i.e. this didn't work in previous version in Java:
+  ```java                
+  // GameEvent is the "base event type"
+  Subscriptions<GameEvent> subsctriptions = new Subscriptions<>(..);
+
+  // GameStarted has GameEvent as parent, the following didn't compile in version 0.17.0 
+  subscriptions.subscribe("ikk", GameStarted.class, gameStarted -> System.out.println("gameStarted: " + gameStarted));
+  ```
+
 ### 0.17.0 (2024-01-19)
 * spring-boot-starter-mongodb no longer autoconfigures itself by just importing the library in the classpath, instead you need to bootstrap by annotating your Spring Boot class with @EnableOccurrent.   
 * Fixed bug in spring-boot-starter-mongodb module in which it didn't automatically configure MongoDB.

dsl/subscription-dsl/blocking/src/main/kotlin/org/occurrent/dsl/subscription/blocking/Subscriptions.kt

@@ -104,16 +104,18 @@ class Subscriptions<E : Any>(private val subscriptionModel: Subscribable, privat
     }
 
     @JvmOverloads
-    fun <E1 : E> subscribe(subscriptionId: String, eventType: Class<E>, startAt: StartAt? = null, fn: Consumer<E1>): Subscription {
+    fun <E1 : E> subscribe(subscriptionId: String, eventType: Class<E1>, startAt: StartAt? = null, fn: Consumer<E1>): Subscription {
         return subscribe(subscriptionId, listOf(eventType), startAt) { e : E ->
+            @Suppress("UNCHECKED_CAST")
             fn.accept(e as E1)
         }
     }
 
     @JvmOverloads
-    fun <E1 : E> subscribe(subscriptionId: String, eventType: Class<E>, startAt: StartAt? = null, fn: BiConsumer<EventMetadata, E>): Subscription {
+    fun <E1 : E> subscribe(subscriptionId: String, eventType: Class<E1>, startAt: StartAt? = null, fn: BiConsumer<EventMetadata, E1>): Subscription {
         return subscribe(subscriptionId, listOf(eventType), startAt) { metadata, e ->
-            fn.accept(metadata, e)
+            @Suppress("UNCHECKED_CAST")
+            fn.accept(metadata, e as E1)
         }
     }