Add a test environment, dynamically update configuration on release

[tofugarden]

Issue description

At the moment we just have the rewrite rules in a root-owned configuration file. This works great, but it means I have to manually update and test everything.

Proposed solution

We should set up a test site, move the configuration to a www-data owned directory, and add webhook to update the site's configuration on tests and releases automatically.

Test site

We can have two virtual hosts: the main holetopia.com and the test site at test.holetopia.com. They shouldn't share configuration at all, and the webhooks and content should react differently to repository events. More later.

Configuration

The rewrite rules should be stored somewhere www-data can read and write them.

Automatic updates

We should add paths that trigger update scripts when called with the proper API key. The update scripts should clone the appropriate tag, and install the new rewrites to the now user-writable directory.

For tests, we should call the hook from an actions workflow file, and then test the rewrites in that same workflow.

For releases, we call the hook from a deployment workflow file, and run tests again just in case.