feat(services/ftp): List dir shows last modified timestamp

[erickguan]

Which issue does this PR close?

Part of #4746.

What changes are included in this PR?

ftp service will also return last modified timestamp.

Are there any user-facing changes?

Nope.

Questions

I found other problems that I want to change but they are not part of the issue.

1. I also found the underlying crate suppaftp supports async. I want to support it. This might be a breaking change for FTP service. Do you consider support async for ftp?

2. I also see sftp implementation uses another crate openssh_sftp_client. I have skimmed through these crates documentation and code. I don't want to expand this comparasion too much. In short, suppaftp depends tls implementation in Rust while openssh_sftp_client depends on OpenSSH. suppaftp has slightly less code. I am considering using suppaftp if that fulfill the current implementation. Happy to discuss more.

3. I tested this locally by using a FTP server in Docker. Roughly put, how much tests do you consider to have and where to start?

[Xuanwo]

Thank you @erickguan for working on this!

[Xuanwo]

1. I also found the underlying crate suppaftp supports async. I want to support it. This might be a breaking change for FTP service. Do you consider support async for ftp?

Hi, ftp already supported async:

opendal/core/src/services/ftp/backend.rs

Lines 333 to 338 in 6e0508d

	async fn read(&self, path: &str, args: OpRead) -> Result<(RpRead, Self::Reader)> {
	let ftp_stream = self.ftp_connect(Operation::Read).await?;
	let reader = FtpReader::new(ftp_stream, path.to_string(), args).await?;
	Ok((RpRead::new(), reader))
	}

Is this what you mean?

2. I also see sftp implementation uses another crate openssh_sftp_client.

I'm not sure what this means. Are you attempting to use suppaftp to connect to an SFTP server?

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Welcome to the start of our discussion. I'm willing to delve deeply into this topic with you. I believe PR comments are not the appropriate place for this.

[erickguan]

@Xuanwo 1. Yes, I had not being accurate. I mean to add the corresponding blocking APIs. For example, blocking_read in your example.

2. Yes, I am proposing to use one crate to support these two services. If you consider worthwhile continuing the thread, I will open a new issue. My bad that suppaftp doesn't support SFTP.

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Welcome to the start of our discussion. I'm willing to delve deeply into this topic with you. I believe PR comments are not the appropriate place for this.

Totally! Thanks for opening the venue for discussions. Created #5214