Provide API to get SPDX license identifier for AspectModelFile

core/esmf-aspect-meta-model-interface/src/main/java/org/eclipse/esmf/aspectmodel/AspectModelFile.java

@@ -46,6 +46,18 @@ default List<String> headerComment() {
       return List.of();
    }
 
+   /**
+    * Returns the SPDX license identifier for this file, if one exists
+    *
+    * @return the SPDX identifier
+    */
+   default Optional<String> spdxLicenseIdentifier() {
+      return headerComment().stream()
+            .filter( line -> line.startsWith( "SPDX-License-Identifier:" ) )
+            .map( line -> line.split( ":" )[1].trim() )
+            .findFirst();
+   }
+
    /**
     * The URI that denominates the source location, if present. It can be a file:// or https:// URL, but it
     * could for example also be an Aspect Model URN, if it refers to a file that is part of the SAMM specification.

core/esmf-aspect-meta-model-java/src/test/java/org/eclipse/esmf/aspectmodel/resolver/AspectModelResolverTest.java

@@ -53,6 +53,7 @@ void testLoadDataModelExpectSuccess() throws URISyntaxException {
          assertThat( result.files().get( 0 ).headerComment() ).isNotNull();
          assertThat( result.files().get( 0 ).headerComment().get( 0 ) ).contains(
                "Copyright (c) 2023 Robert Bosch Manufacturing Solutions GmbH" );
+         assertThat( result.files().get( 0 ).spdxLicenseIdentifier() ).contains( "MPL-2.0" );
       } ).doesNotThrowAnyException();
    }