Introduce new SSO module and tests structure

[LauraBeatris]

Bug fixes

• Fixed the extension of config modules to be exs. Those weren't loading due to being defined as ex.

Summary

• Introduce type specifications to all functions from SSO module. This helps the developers to quickly know what to pass to a function and what to expect to return.
• Restructure module architecture with response structs.
• Use new WorkOS.Client and remove the deprecated WorkOS.API from SSO module.
• Update mix.ex with the modules group. This will be helpful when looking at ExDocs.
• Refactor tests, to have a better Tesla mocking strategy, and assert against status, body, and params.

Usage

{:ok, authorization_url} =
  WorkOS.SSO.get_authorization_url(%{
    provider: "GoogleOAuth",
    redirect_uri: "redirect-uri.com",
    client_id: "client-id"
  })

{:ok, %WorkOS.SSO.ProfileAndToken{access_token: access_token, profile: profile}} =
  WorkOS.SSO.get_profile_and_token(client, %{
    code: "code-123"
  })

{:ok, %WorkOS.SSO.Profile{id: id}} =
  WorkOS.SSO.get_profile(client, %{
    access_token:  "access_token"
 })

{:ok, %WorkOS.SSO.Connection{id: id}} =
  WorkOS.SSO.get_connection(client, "connection-id")

{:ok, %WorkOS.List{}} =
  WorkOS.SSO.list_connections(client, %{})

{:ok, %WorkOS.Empty{}} = WorkOS.SSO.delete_connection(client, "connection-id")