Fix SSL certificate lookup for HTTPS URLs with custom ports

[dicnunz]

Describe your changes

fetchMonitorCertificate now passes the configured HTTPS port to ssl-checker when a monitor URL includes a non-standard port, e.g. https://checkmate.example.org:54321/status. It also still supports the existing monitor.port field and keeps the previous default behavior when no port is configured.

Added a focused regression test for:

• URL port parsed from an HTTPS monitor URL
• monitor.port fallback
• no-port default behavior
• missing certificate expiry error handling

Write your issue number after "Fixes "

Fixes #3646

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• (Do not skip this or your PR will be closed) I deployed the application locally. Server build completed; this is a server utility fix with no UI path changed.
• (Do not skip this or your PR will be closed) I have performed a self-reviewing and testing of my code.
• I have included the issue # in the PR.
• I have added i18n support to visible strings. N/A, no visible strings added.
• I have not included any files that are not related to my pull request, including package-lock and package-json if dependencies have not changed.
• I didn't use any hardcoded values.
• I made sure font sizes, color choices etc are all referenced from the theme. N/A, no UI/CSS changes.
• My PR is granular and targeted to one specific feature.
• I ran npm run format in server and client directories, which automatically formats your code. Touched server files pass Prettier check; no client files changed.
• I took a screenshot or a video and attached to this PR if there is a UI change. N/A, no UI change.

Verification:

• npm test -- --runTestsByPath test/unit/controllers/controllerUtils.test.ts --coverage=false
• npm run build
• npx prettier --check src/controllers/controllerUtils.ts test/unit/controllers/controllerUtils.test.ts
• npx eslint src/controllers/controllerUtils.ts test/unit/controllers/controllerUtils.test.ts (0 errors; test file is ignored by the repo ESLint ignore pattern)

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[ajhollid]

No real problems with this PR, but a small design decision that needs to be considered.

Thanks for your work on the project!

[ajhollid]

I think this should probably be inverted, an explicit port set in the URL should probably take precedence over the monitor.port field.

This is a design decision, but I think the visually prominent port in the monitor URL should take precedence over a field that is not readily visible in the monitor config 🤔

Consider the case where a user has set their url to be https://www.myurl.com:52345/health and accidentally set port 443 on the monitor config. We will silently be checking on 443 while the user would be left wondering why port 52345 as declared in their URL is not responding.

Again a design decision, but I think probably the right call here.

[Br0wnHammer]

LGTM!