Add module-info.java for JPMS support using multi-release JAR (#90)

* Add module-info.java and configure multi-release compilation

Co-authored-by: slachiewicz <6705942+slachiewicz@users.noreply.github.com>

* Move module compilation to java9+ profile activated on JDK 9+

Co-authored-by: slawekjaranowski <3578921+slawekjaranowski@users.noreply.github.com>

* Move module-info.java to src/main/java9 for multi-release JAR

Co-authored-by: slawekjaranowski <3578921+slawekjaranowski@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: slachiewicz <6705942+slachiewicz@users.noreply.github.com>
Co-authored-by: slawekjaranowski <3578921+slawekjaranowski@users.noreply.github.com>
Co-authored-by: Sylwester Lachiewicz <slachiewicz@apache.org>

Author: 3 people

pom.xml

@@ -98,4 +98,48 @@
     </plugins>
   </build>
 
+  <profiles>
+    <profile>
+      <id>java9+</id>
+      <activation>
+        <jdk>[9,)</jdk>
+      </activation>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <executions>
+              <execution>
+                <id>compile-java9</id>
+                <goals>
+                  <goal>compile</goal>
+                </goals>
+                <phase>compile</phase>
+                <configuration>
+                  <release>9</release>
+                  <compileSourceRoots>
+                    <compileSourceRoot>${project.basedir}/src/main/java9</compileSourceRoot>
+                  </compileSourceRoots>
+                  <multiReleaseOutput>true</multiReleaseOutput>
+                </configuration>
+              </execution>
+            </executions>
+          </plugin>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-jar-plugin</artifactId>
+            <configuration>
+              <archive>
+                <manifestEntries>
+                  <Multi-Release>true</Multi-Release>
+                </manifestEntries>
+              </archive>
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
+  </profiles>
+
 </project>

src/main/java9/module-info.java

@@ -0,0 +1,3 @@
+module org.codehaus.plexus.interpolation {
+    exports org.codehaus.plexus.interpolation;
+}