fix: accept underscores in domain hostnames for API URL validation

[Osamaali313]

Changes

PHP's FILTER_VALIDATE_URL rejects underscores in the host portion of a URL, so a service domain such as https://myapp_service.example.com was rejected with "Invalid URL" by the API. The domain could not be saved, Traefik never generated config for it, and the service fell back to a self-signed certificate instead of requesting Let's Encrypt, leaving it unreachable over HTTPS. Underscores are accepted by browsers and Let's Encrypt and are common in Docker service naming.

This adds a small isValidDomainUrl() helper in bootstrap/helpers/domains.php that validates the URL after replacing underscores with hyphens (a valid host character), and routes the docker_compose_domains and fqdn/domain validation in the Applications and Services API controllers through it. URLs without underscores are unaffected, and the existing http/https scheme checks are left unchanged.

Issues

• Fixes [Bug]: URL validator rejects hostnames with underscores, blocking SSL for services (affects docker-compose, Dockerfile, and more) #10597

Category

• Bug fix
• Improvement
• New feature
• Adding new one click service
• Fixing or updating existing one click service

Preview

Not applicable — backend API/validation change, no UI. Behaviour change: a PATCH to /api/v1/applications/{uuid} with a domain containing an underscore is now accepted instead of returning an "Invalid URL" validation error.

AI Assistance

• AI was NOT used to create this PR
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Testing

Validated with unit tests in tests/Unit/IsValidDomainUrlTest.php covering underscore hostnames, ordinary domains/URLs, and invalid inputs; these run as part of the existing Pest suite in CI. Also verified on a local development instance: a service domain containing an underscore now saves successfully instead of being rejected with "Invalid URL". Underscore-free URLs are unaffected.

Contributor Agreement

Important

• I have read and understood the contributor guidelines. If I have failed to follow any guideline, I understand that this PR may be closed without review.
• I have searched existing issues and pull requests (including closed ones) to ensure this isn't a duplicate.
• I have tested all the changes thoroughly with a local development instance of Coolify and I am confident that they will work as expected when a maintainer tests them.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds a centralized URL validator that tolerates underscores in hostnames, and updates API controllers to use it while introducing unit coverage for the underscore regression.

Changes:

• Introduced isValidDomainUrl() helper to validate URLs while allowing underscores in the hostname.
• Replaced direct FILTER_VALIDATE_URL checks in Services/Applications controllers with the new helper.
• Added unit tests covering underscore-host URLs, normal URLs, and invalid inputs.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
tests/Unit/IsValidDomainUrlTest.php	Adds regression/unit tests for underscore-host URL validation.
bootstrap/helpers/domains.php	Introduces isValidDomainUrl() helper used across controllers.
app/Http/Controllers/Api/ServicesController.php	Switches URL validation to isValidDomainUrl().
app/Http/Controllers/Api/ApplicationsController.php	Switches multiple URL validation call sites to isValidDomainUrl().

[andrasbacsai]

Thank you for the PR! 💜