Improve surrogate keys used for V3 endpoints

[notlee]

When we need to purge Fastly cache it can be difficult without purging everything, which we don't want to do.
So let's add surrogate key headers to allow us to purge bundles by:

• language (js/css)
• component (to purge all requests for a component)
• component+version (to purge all requests for a specific component version)

[notlee]

This PR adds surrogate keys to v3 endpoints. I'll leave this issue open as it could be improved by allowing us to purge all urls which contain a specific component or component+version. This would be super helpful in cases where users are including a component with a semver range ^ and we have deployed an important fix to a component.