[5.x] Prevent query parameters bloating the static cache

[duncanmcclean]

This pull request adds a few configuration options to the static_caching.php config file, allowing specifing which query parameters should be allowed/disallowed.

This PR doesn't change the output of Laravel's $request->getUri() or URL::getCurrent() methods. If you need the "normalized" static caching URL, you should call StaticCache::currentUrl().

Note

It's worth noting that while these config options may partially work with full-measure static caching, they're intended for use with half-measure static caching.

New Config Options

• allowed_query_parameters

  • When not empty, this config option will determine which query parameters should be included in the "normalized" static caching URL.
  • For example, if you have the foo query parameter allowed, and visit /contact?foo=bar&david=hasselhoff, it'll serve/write the cached page for /contact?foo=bar.

• disallowed_query_strings

  • When not empty, this config option will determine which query parameters should be excluded from the "normalized" static caching URL.
  • For example, if you have the david query param disallowed, and visit /contact?foo=bar&david=hasselhoff, it'll serve/write the cached page for /contact?foo=bar.

[jasonvarga]

Rather than a new method in the manager class, I've made the getUrl method on the cachers do the work.

This allows the URL to work differently per cacher.

A related issue I noticed while working on this is that since the query string gets alphabetized by Symfony/Laravel, when you use full measure, the generated filename might be different than what you visit.
In the code, /page?a=1&b=1 and /page?b=1&a=1 would be considered the same and both resolve to static/page_a=1&b1.html but to Nginx they would be different. If you visit /page?b=1&a=1 Nginx would look for static/page_b=1&a=1.html which wouldn't exist, so it would fall back to PHP. Statamic would find the normalized file though, and serve the cached version, but you would get a log message that your static cache is not set up correctly.

So, in the file cacher's getUrl method, we can keep the query string in the un-alphabetized order. Also, the allow/disallowed settings would not make sense there since we can't do that in Nginx.