feat: introduce oauth configs into IR, Fern def and OAS extensions

[armandobelardo]

The general idea here is to allow the SDKs to generate helper methods for oauth. We're taking different paths for the different types of oauth:

• Client credentials
• Access code
  • Since this flow typically requires a user to get a short lived access code prior to requesting an access token and refresh token we'd limit this to static helpers:
    • A static helper to generate the authorization URL, the URL a user visits to get the access code, this URL is just constructed by us leveraging the details held within authorization-endpoint
    • A static helper to get the access token from the access code
    • A static helper to refresh a token and get a new access + refresh token
    • If you want to go the extra mile, you could make an object-oriented AccessToken object that takes in the access code with a .get and .refresh token that handle this for the user

[amckinney]

Given that the property is named queryParameters, should we just use http.QueryParameter here instead of defining OauthAuthorizationEndpointParameters?

  QueryParameter:
    extends: commons.Declaration
    properties:
      name: commons.NameAndWireValue
      valueType: types.TypeReference
      allowMultiple: boolean

[amckinney]

nit: Maybe best to standardize on either OAuth* or Oauth. I prefer OAuth*, but fine with either way.