Unstable CustomJpaUserProviderDistTest on Windows

* remove the starting slash from file URI

Closes keycloak#15371

Signed-off-by: Peter Zaoral <pzaoral@redhat.com>

quarkus/tests/integration/src/main/java/org/keycloak/it/utils/RawKeycloakDistribution.java

@@ -25,6 +25,7 @@
 import java.io.InputStreamReader;
 import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
+import java.net.URISyntaxException;
 import java.net.URL;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -530,7 +531,14 @@ public Path getDistPath() {
     }
 
     public void copyProvider(TestProvider provider) {
-        Path providerPackagePath = Paths.get(provider.getClass().getResource(".").getPath());
+        URL pathUrl = provider.getClass().getResource(".");
+        File fileUri;
+        try {
+            fileUri = new File(pathUrl.toURI());
+        } catch (URISyntaxException e) {
+            throw new RuntimeException("Invalid package provider path", e);
+        }
+        Path providerPackagePath = Paths.get(fileUri.getPath());
         JavaArchive providerJar = ShrinkWrap.create(JavaArchive.class, provider.getName() + ".jar")
                 .addClasses(provider.getClasses())
                 .addAsManifestResource(EmptyAsset.INSTANCE, "beans.xml");