Hosting services were only populated when something first made use of

them. This meant that, until that happened, any hosting service URLs

weren't actually registered, and would return a 404.
We now populate when initializing. This incurs a small startup penalty,

but one that would be soon hit anyway, and is necessary for hosting

service URLs to be reliable.
This has been broken since hosting service URLs were introduced in 2.0.

Tested with an HTTP request to a URL as the first-processed request. Before

this change, that request would result in a generic 404. After the change,

I got a suitable error from the hook.