Create official Octue service registry

[cortadocodes]

Feature request

Use Case

We should create an official Octue service registry of our (and/or key) services that can serve as the default service registry. We'll need this in future when we start providing information on how to call each service.

Current state

A service registry is not used by default so a) there's no validation of service revisions and b) revision tags are always required when asking services questions.

Other info

I've removed this placeholder from Service.__init__ for now:

OCTUE_SERVICE_REGISTRY_ENDPOINT = "services.registry.octue.com"

self.service_registries = service_registries or [
    {
        "name": "Octue Registry",
        "endpoint": OCTUE_SERVICE_REGISTRY_ENDPOINT,
    },
]