How do you call a REST API post endpoint (with a file) in Spring Boot?

Question

How would I call a REST API post endpoint that is expecting files and metadata from a Spring Boot application?

Example of what I am trying to call:

@RequestMapping(method = RequestMethod.POST, value = "myUploadService")
public ResponseEntity<String> upload(
  @RequestParam("Files") MultipartFile[] files,
  @RequestParam("AcctNum") String accountNumber,
  @RequestParam("TransId") String transmissionId
) {
  // Logic...
}