Add self-explanation to the model, include the verbal schema description to the flow

[vga91]

When we do calls to the LLM model, today we only pass in the schema.

We want to try to see if there are better results if we also include the "human description" of the schema that we get with apoc.ml.schema (as an option)

perhaps we can also just document how to do this with the existing procedures to augment the prompt with the additional schema.