Document how to customize OpenAPI info per country package

[alexsoble]

As a developer working on building a prototype using OpenFisca, I want to be able to customize the OpenAPI info returned by my API's /spec endpoint.

I see that the OpenFisca-France API includes a custom "contact" field, contact@openfisca.fr:

— https://fr.openfisca.org/api/v21/spec

In my prototype API, the "contact" remains contact@openfisca.org, even though I specified author_email="" in setup.py:

— https://prototype-openfisca-usa-headstart.app.cloud.gov/spec
— https://github.com/18F/prototype-openfisca-usa-headstart/blob/master/setup.py#L9

I would ideally want to see this documentation under "OpenAPI specification configuration": https://openfisca.org/doc/openfisca-web-api/config-openapi.html.

If someone can point me in the right direction for how to customize this OpenAPI config, I'd be more than happy to open a PR that adds instructions to the docs! 😄

[MattiSG]

This already has to be implemented, see openfisca/openfisca-core#1207.