Use Annotated[pydantic.AnyUrl, pydantic.UrlConstraints(host_required=False)] instead of AnyUrl

[dsp-ant]

Pydantic's AnyUrl requires a host to be specified. For file resources this means that a triple slash such as file:///foo.txt is required because there is no host. We should likely be using Annotated[pydantic.AnyUrl, pydantic.UrlConstraints(host_required=False)] or something along these lines.