Add security to FTP

[Maninda]

Purpose

Resolves ballerina-platform/ballerina-library#1438

Checklist

• Linked to an issue
• Updated the changelog
• Added tests

[codecov]

Codecov Report

Merging #276 (a6c9d4a) into master (13e4249) will increase coverage by 3.13%.
The diff coverage is 68.75%.

@@             Coverage Diff              @@
##             master     #276      +/-   ##
============================================
+ Coverage     73.50%   76.64%   +3.13%     
- Complexity       67       70       +3     
============================================
  Files            18       18              
  Lines           785      762      -23     
  Branches        125      120       -5     
============================================
+ Hits            577      584       +7     
+ Misses          181      155      -26     
+ Partials         27       23       -4     

Impacted Files	Coverage Δ
ftp-ballerina/commons.bal	100.00% <ø> (+45.00%)	⬆️
...rg/ballerinalang/stdlib/ftp/util/FTPConstants.java	100.00% <ø> (ø)
ftp-ballerina/client_endpoint.bal	95.83% <50.00%> (-0.09%)	⬇️
...org/ballerinalang/stdlib/ftp/client/FTPClient.java	76.92% <61.53%> (+3.38%)	⬆️
...ava/org/ballerinalang/stdlib/ftp/util/FTPUtil.java	58.22% <66.66%> (+0.72%)	⬆️
...erinalang/stdlib/ftp/server/FTPListenerHelper.java	79.06% <75.00%> (+17.70%)	⬆️
ftp-ballerina/external_functions.bal	85.71% <100.00%> (ø)
ftp-ballerina/listener_endpoint.bal	85.18% <100.00%> (-1.03%)	⬇️
...g/ballerinalang/stdlib/ftp/server/FTPListener.java	81.08% <0.00%> (+5.40%)	⬆️
...erinalang/stdlib/ftp/client/FTPClientListener.java	100.00% <0.00%> (+14.28%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 13e4249...a6c9d4a. Read the comment docs.