Generates swagger.json file based on phoenix router and controllers.

Usage:

mix phx.swagger.generate

Swagger file configuration must be defined in the project config, eg:

config :your_app, :phoenix_swagger,
  swagger_files: %{
    "priv/static/swagger.json" => [router: YourAppWeb.Router, endpoint: YourAppWeb.Endpoint]
    # ... additional swagger files can be added here
  }