GH-846 - Fix module identifier lookup for jMolecules @Module(id = …).

We now properly translate jMolecules' @Module declaration configuring the id attribute explicitly into the identifier used for an application module.

Introduce @ApplicationModule(id = …) for Spring Modulith-native identifier customization.

spring-modulith-api/src/main/java/org/springframework/modulith/ApplicationModule.java

@@ -32,6 +32,13 @@ public @interface ApplicationModule {
 
 	public static final String OPEN_TOKEN = "¯\\_(ツ)_/¯";
 
+	/**
+	 * The identifier of the module. Must not contain a double colon ({@code ::}).
+	 *
+	 * @return will never be {@literal null}.
+	 */
+	String id() default "";
+
 	/**
 	 * The human readable name of the module to be used for display and documentation purposes.
 	 *