Implement file renaming functionality to support custom filenames

[ChamroeunProMaxQ]

This PR introduces the ability to rename uploaded files before saving them to local storage, addressing the feature request outlined in Issue #14.

Changes:

Added filename callback: A new filename option has been introduced in the FormDataInterceptorConfig interface. This callback allows users to define custom filenames for uploaded files.

filename: (originalName: string) => string;

If not provided, the system generates a unique filename by appending a salt to the original name.

Updated FileSystemStoredFile class: The FileSystemStoredFile class now accepts the filename callback. If the callback is provided in the configuration, it is used to determine the file's name before saving.

static async create(
busboyFileMeta: ParticleStoredFile,
stream: ReadableStream,
config: FormDataInterceptorConfig
): Promise<FileSystemStoredFile> {
const fileName = config.filename
  ? config.filename(busboyFileMeta.originalName)
  : FileSystemStoredFile.makeFileNameWithSalt(busboyFileMeta.originalName);
}

Benefits

• Customizable filenames: Define naming conventions for uploaded files.
• Prevent collisions: Unique names reduce the risk of overwriting existing files.
• Safe for Linux/Ubuntu: Long or unsafe filenames are truncated and sanitized.
• Improved file management: Filenames can include relevant metadata for easier identification.