chore(nextjs): Add tests covering the new middleware matcher - #3741

Description

The matcher we currently document breaks Clerk for the following scenario.

• Have an app using the currently documented matcher
• Have a URL structure similar to /articles/:article-slug. :article-slug would be something like ${article_title}_${article_id} , eg: /article/hello-team-support_123a - pretty common stuff so far.

If an article contains a . in its name, eg /article/i-use-clerk.com-and-why-you-should-too_123, then auth() and related helpers will fail because the matcher will not match the request URL and the middleware will be skipped.

This bug recently hit a few customers. This PR updates the matcher with a simplified version that no longer handles files as an edge case. We want to update our own dashboard first to further test the new matcher, before we reach out to the customers with the updated version.

The new matcher works for all cases tested in this PR. In comparison, the old matcher we used (shown below) failed for at least the following cases:

    ✕ triggers the middleware for "/sl.ug-123" (1 ms)
    ✕ triggers the middleware for "/sl.ug"
    ✕ triggers the middleware for "/download?filename=1.jpg"
    ✕ triggers the middleware for "/download/?filename=1.jpg" (1 ms)
    ✕ triggers the middleware for "/download?test=1&filename=1.jpg"
    ✕ triggers the middleware for "/download?filename=1.jpg&test=1"
    ✕ triggers the middleware for "/download?filename=1.png&test=1"
    ✕ triggers the middleware for "/file.json" (1 ms)
    ✕ triggers the middleware for "/file.json/"
    ✕ triggers the middleware for "/a/b.json"

Important: any change here needs to be reflected in the docs + the dashboard quickstart page.

For reference, the old matcher was:

export const config = {
  matcher: ['/((?!.*\\..*|_next).*)', '/', '/(api|trpc)(.*)'],
};

Checklist

• npm test runs as expected.
• npm run build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other: