It is a relatively common desire to want to have static values
available to all the solids in a pipeline. The way to model this is to
have a resource that ends up being the configuration value itself.
Without a specific top-level API, this is actually quite non-obvious.
This adds a new top-level api value_resource that does exactly that.
It takes a config_schema argument. It ensure that value pass in via
config fulfills that value and then makes the resource the config
value itself. There one can do something like fill out a dictionary in
config and have that dictionary avaiable across the pipeline.