Add a FileUpload Plugin

[SentryMan]

• Adds new methods to Context to set/retrieve objects in the attributes by their class
• new module for file uploads
• file upload plugin adds a filter that sets a file upload service into the request attributes

(not sure about the class/method names)

// Example: Registering the plugin with a custom configuration
var jex = Jex.create();
var uploadPlugin = FileUploadPlugin.create(config -> {
    // Set the maximum file size for a single upload to 50 MB
    config.maxFileSize(50, SizeUnit.MB);
    // Set the cache directory for large files
    config.cacheDirectory("/var/tmp/jex-uploads");
});
jex.register(uploadPlugin);

Within the route handlers, you can then retrieve the io.avaje.jex.file.upload.FileUploadService from the context attributes and use it to access the uploaded files.

// Example: Handling a file upload in a POST route
jex.post("/upload", ctx -> {
    // Get the FileUploadService from the request context
    FileUploadService service = ctx.attribute(FileUploadService.class);
    // Retrieve the uploaded file using its form field name
    MultiPart uploadedFile = service.uploadedFile("image-file");

    if (uploadedFile != null) {
        System.out.println("File name: " + uploadedFile.filename());

    }
    ctx.status(200).result("File upload successful!");
});

resolves #302