Add CI to validate schemas against a document sample

[acmiyaguchi]

This was once handled by the edge-validator docker image, but has posed significant challenges in terms of data leaving the GCP environment. We should still include CI of this form because it increases our confidence in the deployment of schemas here.

One way that would limit issues is to provision a cloudfunction that provides an api to test validation errors against a schema version. CI would be provided a service account to authenticate with this service, which should only reveal information about validation errors.