[client] Add env var to skip DNS probing

[lixmal]

Describe your changes

Issue ticket number and link

Stack

Checklist

• Is it a bug fix
• Is a typo/documentation fix
• Is a feature enhancement
• It is a refactor
• Created tests that fail without the change (if possible)

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Documentation

Select exactly one:

• I added/updated documentation for this change
• Documentation is not needed for this change (explain why)

Docs PR URL (required if "docs added" is checked)

Paste the PR link from https://github.com/netbirdio/docs here:

https://github.com/netbirdio/docs/pull/__

Summary by CodeRabbit

New Features

• DNS probing can now be skipped via environment variable configuration for advanced deployments that don't require DNS validation.

[coderabbitai]

📝 Walkthrough

Walkthrough

Modified DNS probing behavior to support environment-driven skipping. Added a public constant NB_SKIP_DNS_PROBE that, when set to a truthy value, causes the ProbeAvailability function to return early without performing DNS probing. Includes logging for invalid values and successful skip events.

Changes

Cohort / File(s)	Summary
DNS Probing Configuration client/internal/dns/server.go	Added public constant NB_SKIP_DNS_PROBE and conditional logic in ProbeAvailability to skip DNS probing when the environment variable is set to a truthy value. Includes warning logs for invalid boolean values and info logs when skipping occurs. Added imports for os and strconv.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

Poem

🐰 A little flag to skip the probe,
DNS rests in burrows so deep,
When NB_SKIP_DNS_PROBE is shown,
Through environment's door we creep,
Faster hops, no DNS to keep! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding an environment variable to skip DNS probing in the client.
Description check	✅ Passed	The description follows the template structure with completed checklist items and documentation decision, but the 'Describe your changes' section lacks detail about what the env var does.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch env-skip-dns-probe

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[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