Add FTPS with SSL/TLS configuration

[YasanPunch]

Purpose

---

Fixes: ballerina-platform/ballerina-library/#8489

Adds FTPS (FTP over SSL/TLS) support to the FTP module, enabling secure file transfers using SSL/TLS certificates.

Changes:

Added FTPS protocol option to the Protocol enum
Added SecureSocket configuration type for FTPS SSL/TLS settings
Added FtpsMode enum to support IMPLICIT and EXPLICIT FTPS modes

public enum Protocol {
    FTP = "ftp",
    FTPS = "ftps",  // New: Secure File Transfer Protocol
    SFTP = "sftp"
}

# FTPS connection mode
public enum FtpsMode {
    IMPLICIT,   // SSL/TLS established immediately (port 990)
    EXPLICIT    // Upgrades to SSL/TLS via AUTH TLS (port 21)
}

# Secure socket configuration for FTPS
public type SecureSocket record {|
    crypto:KeyStore key?;
    crypto:TrustStore trustStore?;
    FtpsMode mode = EXPLICIT;
|};

public type AuthConfiguration record {|
    ...
    SecureSocket secureSocket?;  // New: For FTPS protocol
|};

(Current) Usage Example:

ftp:ClientConfiguration ftpsConfig = {
    protocol: ftp:FTPS,
    host: "ftps.example.com",
    port: 21,
    auth: {
        credentials: {username: "user", password: "pass"},
        secureSocket: {
            key: {path: "client.p12", password: "keypass"},
            trustStore: {path: "truststore.p12", password: "trustpass"},
            mode: ftp:EXPLICIT
        }
    }
};

Future Enhancements (TODO):

• Data channel protection level configuration (PROT P/C/S/E)
• Hostname verification toggle for enhanced security
• Test case development

Checklist

• Linked to an issue
• Updated the changelog
• Added tests
• Updated the spec
• Checked native-image compatibility

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

❌ Patch coverage is 7.43982% with 423 lines in your changes missing coverage. Please review.
✅ Project coverage is 19.01%. Comparing base (dec8c19) to head (c9b7c36).

Files with missing lines	Patch %	Lines
.../ftp/transport/server/util/FileTransportUtils.java	7.89%	132 Missing and 8 partials ⚠️
...java/io/ballerina/stdlib/ftp/client/FtpClient.java	15.62%	97 Missing and 11 partials ⚠️
...ballerina/stdlib/ftp/server/FtpListenerHelper.java	0.00%	102 Missing ⚠️
...ain/java/io/ballerina/stdlib/ftp/util/FtpUtil.java	1.88%	51 Missing and 1 partial ⚠️
...ftp/transport/server/RemoteFileSystemConsumer.java	0.00%	20 Missing ⚠️
...connector/contractimpl/VfsClientConnectorImpl.java	50.00%	0 Missing and 1 partial ⚠️

❌ Your project status has failed because the head coverage (19.01%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #1516       +/-   ##
=============================================
- Coverage     81.17%   19.01%   -62.17%     
+ Complexity      509      243      -266     
=============================================
  Files            40       55       +15     
  Lines          2561     3518      +957     
  Branches        407      622      +215     
=============================================
- Hits           2079      669     -1410     
- Misses          319     2746     +2427     
+ Partials        163      103       -60     

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[sonarqubecloud]

Quality Gate passed

Issues
17 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
2.5% Duplication on New Code

See analysis details on SonarQube Cloud