GH-817 - Properly guard for presence of jMolecules' @module type.

As @module is absent from the Kotlin flavor of jMolecules, code that refers to that is now guarded with a more specific check for that type in particular.

Author: odrotbohm

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModuleInformation.java

@@ -44,7 +44,7 @@ public static ApplicationModuleInformation of(JavaPackage javaPackage) {
 
 		var rootPackage = javaPackage.toSingle();
 
-		return JMoleculesTypes.isPresent() && JMoleculesModule.supports(rootPackage)
+		return JMoleculesTypes.isModulePresent() && JMoleculesModule.supports(rootPackage)
 				? new JMoleculesModule(rootPackage)
 				: new SpringModulithModule(rootPackage);
 	}

spring-modulith-core/src/main/java/org/springframework/modulith/core/Types.java

@@ -51,21 +51,35 @@ static class JMoleculesTypes {
 		private static final String MODULE = ANNOTATION_PACKAGE + ".Module";
 
 		private static final boolean PRESENT = ClassUtils.isPresent(AT_ENTITY, JMoleculesTypes.class.getClassLoader());
+		private static final boolean MODULE_PRESENT = ClassUtils.isPresent(MODULE, JMoleculesTypes.class.getClassLoader());
 
 		static final String AT_DOMAIN_EVENT_HANDLER = BASE_PACKAGE + ".event.annotation.DomainEventHandler";
 		static final String AT_DOMAIN_EVENT = BASE_PACKAGE + ".event.annotation.DomainEvent";
 		static final String DOMAIN_EVENT = BASE_PACKAGE + ".event.types.DomainEvent";
 
+		/**
+		 * Returns whether jMolecules is generally present.
+		 *
+		 * @see #isModulePresent()
+		 */
 		public static boolean isPresent() {
 			return PRESENT;
 		}
 
+		/**
+		 * Returns whether the jMolecules {@link Module} type is present. We need to guard for this explicitly as the Kotlin
+		 * variant of jMolecules DDD does not ship that type.
+		 */
+		public static boolean isModulePresent() {
+			return MODULE_PRESENT;
+		}
+
 		@Nullable
 		@SuppressWarnings("unchecked")
 		public static Class<? extends Annotation> getModuleAnnotationTypeIfPresent() {
 
 			try {
-				return isPresent()
+				return isModulePresent()
 						? (Class<? extends Annotation>) ClassUtils.forName(MODULE, JMoleculesTypes.class.getClassLoader())
 						: null;
 			} catch (Exception o_O) {