Add resource loader method to get base URL

This will allow for easier construction of protection domains for class loading, and may be useful in other contexts.

resource/src/main/java/io/smallrye/common/resource/JarFileResourceLoader.java

@@ -75,6 +75,10 @@ public Resource findResource(final String path) {
         }
     }
 
+    public URL baseUrl() {
+        return base;
+    }
+
     public void close() {
         try {
             jarFile.close();

resource/src/main/java/io/smallrye/common/resource/PathResourceLoader.java

@@ -2,6 +2,8 @@
 
 import java.io.Closeable;
 import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
 import java.nio.file.FileSystem;
 import java.nio.file.Path;
 
@@ -42,6 +44,15 @@ public Resource findResource(final String path) {
         return new PathResource(canon, base.resolve(canon));
     }
 
+    public URL baseUrl() {
+        try {
+            return base.toUri().toURL();
+        } catch (MalformedURLException e) {
+            throw new UnsupportedOperationException(
+                    "Base URL is not supported for this loader because the path does not have a valid URL", e);
+        }
+    }
+
     public void close() {
         Closeable c = this.c;
         if (c != null) {

resource/src/main/java/io/smallrye/common/resource/ResourceLoader.java

@@ -2,6 +2,7 @@
 
 import java.io.Closeable;
 import java.io.IOException;
+import java.net.URL;
 
 /**
  * A loader which can find resources by their path.
@@ -22,6 +23,13 @@ public interface ResourceLoader extends Closeable {
      */
     Resource findResource(String path) throws IOException;
 
+    /**
+     * {@return the base URL for this loader}
+     */
+    default URL baseUrl() {
+        throw new UnsupportedOperationException("Base URL is not supported by this resource loader");
+    }
+
     /**
      * Get a child resource loader for the given child path.
      * This method always returns a resource loader, even if the path does not exist.

resource/src/main/java/io/smallrye/common/resource/URLResourceLoader.java

@@ -26,4 +26,8 @@ public Resource findResource(final String path) throws IOException {
         String canon = ResourceUtils.canonicalizeRelativePath(path);
         return new URLResource(canon, new URL(base, canon));
     }
+
+    public URL baseUrl() {
+        return base;
+    }
 }