[Master] Add custom headers and parameters to the unsubscription request

[ayeshLK]

Purpose

$subject

Part of: #4795

Examples

N/A

Checklist

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

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% 🎉

Comparison is base (45a3f82) 87.26% compared to head (f78bace) 87.27%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #636      +/-   ##
============================================
+ Coverage     87.26%   87.27%   +0.01%     
  Complexity       38       38              
============================================
  Files            15       15              
  Lines           730      731       +1     
  Branches        356      356              
============================================
+ Hits            637      638       +1     
  Misses           88       88              
  Partials          5        5              

Files Changed	Coverage Δ
ballerina/annotation.bal	80.00% <ø> (ø)
ballerina/subscriber_client.bal	98.00% <100.00%> (+0.04%)	⬆️

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