GH-578 - Support for nested application modules.

The ApplicationModules bootstrap now triggers the module base package detection, followed by a new, additional pass of detecting nested application module packages. Those packages are now added to the ones we create ApplicationModule instances for and also handed into the module instance creation step as exclusions to make sure that parent modules do not include code residing in sub-modules.

The bootstrap of ApplicationModules now uses a dedicated ApplicationModuleSource to allow calculating a default module name relative to the application base package.

Each module now operates on the Classes instance obtained from the JavaPackage instance that constitutes the module's base package but filtered by the given exclusions.

spring-modulith-core/src/test/java/empty/EmptyApplication.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package empty;
+
+import org.springframework.modulith.Modulithic;
+
+/**
+ * @author Oliver Drotbohm
+ */
+@Modulithic
+public class EmptyApplication {}