improvement: add in config to enrich pypi metadata

[armandobelardo]

This allow for configuring package metadata at the

Top level:

api: ./openapi.yml
metadata:
  description: this is the desc for my package
  authors:
     - email: support@buildwithfern.com
        name: Armando

Group level:

...
groups:
  my_group:
    metadata:
      description: this is the desc for my package
      authors:
       - email: support@buildwithfern.com
          name: Armando
    generators:
      - name: fernapi/fern-python-sdk
         ...

And finally the actual generator, which allows you to specify more metadata, specific to the output location:

...
groups:
  my_group:
    generators:
      - name: fernapi/fern-python-sdk
         metadata:
            description: this is the desc for my package
            keywords:
              - science
              - data analysis
            documentationLink: ""
            homepageLink: ""
            authors:
              - email: support@buildwithfern.com
                 name: Armando
         ...

If you configure at multiple levels, the more specific layer takes precedent

[dsinghvi]

i read through the code and it looks right to me but i think it would be great if we could write a snapshot test to make sure that convertGeneratorsConfiguration works how we want it to (snapshot the outputs)