fix: close HTTP response body in health check for core-keeper

[remo-lab]

Fixes a resource leak in the Core Keeper registry health check where the HTTP response body was not closed.
Since health checks run periodically per registered service, this caused file descriptors to accumulate over time, potentially leading to “too many open files” errors.
The fix ensures the response body is always closed on all execution paths. Unit tests were added to validate the behavior.

Fixes #5327

✔️ ✔️

The Core Keeper registry health check performs periodic HTTP requests for each registered service but did not close the HTTP response body on any execution path.
Since these checks run continuously in background goroutines, the unclosed response bodies caused file descriptors to accumulate over time.
In production deployments with multiple services, this could lead to file descriptor exhaustion, resulting in failed HTTP requests, degraded health monitoring, or service instability.
Closing the response body on all paths prevents this resource leak without altering existing behavior.

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ❌] I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• [❌ ] I am not introducing a new dependency (add notes below if you are)
• [✔️ ] I have added unit tests for the new feature or bug fix (if not, why?)
• [✔️ ] I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• I have opened a PR for the related docs change (if not, why?)

Testing Instructions

Run unit tests:

go test ./internal/core/keeper/registry/... -v
screenshot of terminal after the fix:
<img width="1191" height="1250" alt="image" src="https://github.com/user-attachments/assets/778600b0-0d6b-4c12-b192-b72e03b1ae88" />

[remo-lab]

Hi @judehung , This PR addresses a file descriptor leak in the Core Keeper registry health check and includes unit tests to verify the fix. Please let me know if any changes are needed. Thanks!

[judehung]

@remo-lab

Thanks for the fix—your changes look reasonable to me. However, registry_test.go is not formatted according to gofmt, which is causing the PR checks to fail.

You can run the following command in your environment to format registry_test.go correctly.:

 gofmt -w ./internal/core/keeper/registry/registry_test.go

[judehung]

Please update the copyright header to the correct year

Suggested change

	// Copyright (C) 2024 IOTech Ltd
	// Copyright (C) 2025 IOTech Ltd

[remo-lab]

Hi @judehung ,Thanks for the review! I've addressed your feedback:

• Updated the copyright year from 2024 to 2025 in registry_test.go
• Verified formatting with gofmt -w - the file was already correctly formatted, so no changes were needed there.
  screenshot of terminal:

The copyright year is now updated. Please let me know if there's anything else that needs to be addressed.

[judehung]

@remo-lab
To comply with Semantic PR requirements, please update the PR title and commit messages to:

fix: close HTTP response body in health check for core-keeper

Note that registry is not a valid scope as defined in this repository.

[remo-lab]

HI @judehung ,Thanks for the review and guidance. I’ve updated the PR title and squashed the commits to comply with the Semantic PR requirements. Please let me know if anything else needs adjustment.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud

[judehung]

Thanks for the fix. LGTM