Fix: Duplicate File Parts Generated in MockMvc using MockPart

[Lee-WonJun]

PR for Issue #953

Solution:

1. Compare if the File and Part contain the same content. If they do, remove one of them (assuming they are paired, so once removed, it will not be compared again).
2. If they are not the same, add the part to the parts list.
3. The MockPart implementation itself calls setContentDispositionFormData, which is only added to Part. Therefore, when comparing, setContentDispositionFormData is also included in the comparison.

Reference Code (MockPart):

public MockPart(String name, @Nullable String filename, @Nullable byte[] content, @Nullable MediaType contentType) {
		Assert.hasLength(name, "'name' must not be empty");
		this.name = name;
		this.filename = filename;
		this.content = (content != null ? content : new byte[0]);
		this.headers.setContentDispositionFormData(name, filename);
		this.headers.setContentType(contentType);
	}

Additional Information:

I initially wrote a test code to compare the MediaType content type, but due to compatibility checks, I could not use the MockPart constructor that allows defining contentType (introduced in @since 6.1.2). As a result, I removed it from the test.

[wilkinsona]

Thanks for the PR, but it's too early to consider possible fixes for #953. It's not yet clear if a change in REST Docs is even the right thing to do.