Create webhook and CI status for StorageServer caching

To address issues around storage server caching delay, we should preload new resources into the storage server by triggering a CI run on PRs to General. I'm thinking we have a webhook that triggers the StorageServer into caching any new resources mentioned in the current pull request, and then if they all get cached successfully, we push a status to the PR that sets a passing status to that CI status.

This should allow us to pre-fill the storage server's cache so that when the PR is merged, the resources are already stored.

No files, tests, or entry points are named. Start by locating the General pull-request webhook and CI status integrations, then trace how the StorageServer receives resource requests. Done means a PR can trigger caching of its new resources and receives a passing status only after caching succeeds.

Written by the indexing model from the issue text.