refactor(paper): avoid use of default maven central URL

bukkit/src/main/java/net/william278/husksync/PaperHuskSyncLoader.java

@@ -34,6 +34,7 @@ import org.jetbrains.annotations.Nullable;
 import java.io.InputStream;
 import java.util.List;
 import java.util.Objects;
+import java.util.stream.Stream;
 
 @NoArgsConstructor
 @SuppressWarnings("UnstableApiUsage")
@@ -46,13 +47,20 @@ public class PaperHuskSyncLoader implements PluginLoader {
         resolveLibraries(classpathBuilder).stream()
                 .map(DefaultArtifact::new)
                 .forEach(artifact -> resolver.addDependency(new Dependency(artifact, null)));
-        resolver.addRepository(new RemoteRepository.Builder(
+        resolver.addRepository(new RemoteRepository.Builder("maven", "default", getMavenUrl()).build());
-                "maven", "default", "https://repo.maven.apache.org/maven2/"
-        ).build());
 
         classpathBuilder.addLibrary(resolver);
     }
 
+    @NotNull
+    private static String getMavenUrl() {
+        return Stream.of(
+                System.getenv("PAPER_DEFAULT_CENTRAL_REPOSITORY"),
+                System.getProperty("org.bukkit.plugin.java.LibraryLoader.centralURL"),
+                "https://maven-central.storage-download.googleapis.com/maven2"
+        ).filter(Objects::nonNull).findFirst().orElseThrow(IllegalStateException::new);
+    }
+
     @NotNull
     private static List<String> resolveLibraries(@NotNull PluginClasspathBuilder classpathBuilder) {
         try (InputStream input = getLibraryListFile()) {